Radiation-sensitive resin composition, resist pattern-forming method and polymer composition

ABSTRACT

Provided are a radiation-sensitive resin composition, a resist pattern-forming method and a polymer component. The radiation-sensitive resin composition contains: a polymer component having a first structural unit that includes a phenolic hydroxyl group and a second structural unit that includes an acid-labile group; and a radiation-sensitive acid generator, wherein, the polymer component satisfies inequality (A), wherein, in the inequality (A), X1 represents a proportion (mol %) of the first structural unit comprised with respect to total structural units constituting the polymer component included in a fraction eluted until a retention time at which a cumulative area accounts for 1% of a total area on a gel permeation chromatography (GPC) elution curve of the polymer component detected by a differential refractometer; and X2 represents a proportion (mol %) of the first structural unit comprised with respect to total structural units constituting the polymer component. 
       X1&lt;X2   (A)

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a radiation-sensitive resincomposition, a resist pattern-forming method and a polymer composition.

DESCRIPTION OF THE RELATED ART

A radiation-sensitive composition for use in microfabrication bylithography generates an acid at a light-exposed region upon anirradiation with a radioactive ray, e.g., an electromagnetic wave suchas a far ultraviolet ray such as an ArF excimer laser beam, a KrFexcimer laser beam, etc., an extreme ultraviolet ray (EUV), or a chargedparticle ray such as an electron beam. A chemical reaction in which theacid serves as a catalyst causes the difference in rates of dissolutionin a developer solution, between light-exposed regions andlight-unexposed regions, whereby a resist pattern is formed on asubstrate.

Such a radiation-sensitive resin composition is demanded to be favorablein sensitivity to exposure light such as EUV or an electron beam andalso superior in not only resolution but also a LWR (Line WidthRoughness) performance, thereby enabling a highly accurate pattern to beobtained. To address the demands, the structure of the polymer containedin the radiation-sensitive resin composition has been extensivelystudied, and it is known that incorporation of a lactone structure suchas a butyrolactone structure and a norbornanelactone structure canimprove these performances (see Japanese Unexamined Patent Application,Publication Nos. H11-212265, 2003-5375 and 2008-83370).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Unexamined Patent Application, PublicationNo. H11-212265

Patent Document 2: Japanese Unexamined Patent Application, PublicationNo. 2003-5375

Patent Document 3: Japanese Unexamined Patent Application, PublicationNo. 2008-83370

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, under current circumstances in which miniaturization of resistpatterns has proceeded to a level for line widths of no greater than 40nm, required levels for the aforementioned performances are furtherelevated, and the conventional radiation-sensitive resin compositiondescribed above is not capable of meeting these demands. Moreover,miniaturization of resist patterns is recently accompanied by inparticular, demands for inhibition of generation of defects in theresist patterns.

The present invention was made in view of the foregoing circumstances,and an object of the invention is to provide a radiation-sensitive resincomposition, a resist pattern-forming method and a polymer compositionbeing superior in inhibitory ability of defects and in LWR performanceswhile the sensitivity is maintained.

Means for Solving the Problems

According to one aspect of the invention made for solving theaforementioned problems, a radiation-sensitive resin compositioncontains:

a polymer component (hereinafter, may be also referred to as “(A)polymer component” or “polymer component (A)”) having in a singlepolymer or different polymers, a first structural unit that includes aphenolic hydroxyl group (hereinafter, “structural unit (I)”hereinafter,may be also referred to as), and a second structural unit that includesan acid-labile group (hereinafter, may be also referred to as“structural unit (II)”);

and a radiation-sensitive acid generator (hereinafter, may be alsoreferred to as “(B) acid generator” or “acid generator (B)”)

wherein, the polymer component (A) satisfies the following inequality(A):

X1<X2   (A)

wherein, in the inequality (A), X1 represents a proportion (mol %) ofthe first structural unit included with respect to total structuralunits constituting the polymer component included in a fraction eluteduntil a retention time at which a cumulative area accounts for 1% of atotal area on a gel permeation chromatography (GPC) elution curve of thepolymer component detected by a differential refractometer; and X2represents a proportion (mol %) of the first structural unit includedwith respect to total structural units constituting the polymercomponent.

According to other aspect of the invention made for solving theaforementioned problems, a radiation-sensitive resin compositioncontains:

a polymer component (polymer component (A)) having in a single polymeror different polymers, a first structural unit that includes a phenolichydroxyl group (structural unit (I)) and a second structural unit thatincludes an acid-labile group (structural unit (II)); and

a radiation-sensitive acid generator (acid generator (B)),

wherein the polymer component (A)satisfies the following inequality (B):

$\begin{matrix}{\frac{X\; 2}{X\; 1} > 1.0} & (B)\end{matrix}$

wherein, in the inequality (B), X1 represents a proportion (mol %) ofthe first structural unit included with respect to total structuralunits constituting the polymer component included in a fraction eluteduntil a retention time at which a cumulative area accounts for 1% of atotal area on a gel permeation chromatography (GPC) elution curve of thepolymer component detected by a differential refractometer; and X2represents a proportion (mol %) of the first structural unit comprisedwith respect to total structural units constituting the polymercomponent.

According to still other aspect of the invention made for solving theaforementioned problems, a resist pattern-forming method includes:applying the radiation-sensitive resin composition of the above aspectdirectly or indirectly on a substrate; exposing a resist film providedby the applying; and developing the resist film exposed.

According to yet other aspect of the invention made for solving theaforementioned problems, a polymer composition contains a polymercomponent having in a single polymer or different polymers, a firststructural unit that includes a phenolic hydroxyl group and a secondstructural unit that includes an acid-labile group,

wherein, the polymer component satisfies the following inequality (A):

X1<X2   (A)

wherein, in the inequality (A), X1 represents a proportion (mol %) ofthe first structural unit included with respect to total structuralunits constituting the polymer component included in a fraction eluteduntil a retention time at which a cumulative area accounts for 1% of atotal area on a gel permeation chromatography (GPC) elution curve of thepolymer component detected by a differential refractometer; and X2represents a proportion (mol %) of the first structural unit includedwith respect to total structural units constituting the polymercomponent.

According to a further aspect of the invention made for solving theaforementioned problems, a polymer composition contains a polymercomponent having in a single polymer or different polymers, a firststructural unit that includes a phenolic hydroxyl group and a secondstructural unit that includes an acid-labile group,

the polymer component satisfies inequality (B):

$\begin{matrix}{\frac{X\; 2}{X\; 1} > 1.0} & (B)\end{matrix}$

wherein, in the inequality (B), X1 represents a proportion (mol %) ofthe first structural unit included with respect to total structuralunits constituting the polymer component included in a fraction eluteduntil a retention time at which a cumulative area accounts for 1% of atotal area on a gel permeation chromatography (GPC) elution curve of thepolymer component detected by a differential refractometer; and X2represents a proportion (mol %) of the first structural unit includedwith respect to total structural units o constituting the polymercomponent.

Effects of the Invention

The radiation-sensitive resin composition and the resist pattern-formingmethod of the aspects of the present invention enable a resist patternwith less LWR and fewer defects to be formed while the sensitivity ismaintained. The polymer composition of the aspect of the presentinvention can be suitably used as a component of the radiation-sensitiveresin composition of the above aspect of the invention. Therefore, thesecan be suitably used in manufacture of semiconductor devices in whichfurther progress of miniaturization is expected in the future.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a fraction (fraction A) eluted until aretention time at which a cumulative area accounts for 1% of a totalarea on a gel permeation chromatography (GPC) elution curve incalculating X1.

DESCRIPTION OF THE EMBODIMENTS Radiation-Sensitive Resin Composition

The radiation-sensitive resin composition of one embodiment of thepresent invention contains the polymer component (A) and the acidgenerator (B). The radiation-sensitive resin composition typicallycontains a solvent (hereinafter, may be also referred to as “(D)solvent” or “solvent (D)”). In addition, the radiation-sensitive resincomposition may also contain as a favorable component, an acid diffusioncontroller (hereinafter, may be also referred to as “(C) acid diffusioncontroller” or “acid diffusion controller (C)”), and may further containother optional component(s) within a range not leading to impairment ofthe effects of the present invention.

The radiation-sensitive resin composition is superior in inhibitoryability of defects and in LWR performances while the sensitivity ismaintained. Although not necessarily clarified and without wishing to bebound by any theory, the reason for achieving the effects describedabove due to the radiation-sensitive resin composition having theaforementioned constitution is inferred as in the following, forexample. The present inventors have found that a component having a highmolecular weight having a great proportion of the structural unit (I)contained may cause defects. As a result of thorough investigations inview of such findings, the present inventors found that theaforementioned effects are achieved when the polymer component (A)having in a single polymer or different polymers, the structural unit(I) that includes a phenolic hydroxyl group, and the structural unit(II) that includes an acid-labile group is used, in which the proportion(X1) of the structural unit (I) falling under a high-molecular weightregion is less than the proportion (X2) of the structural unit (I)included with respect to total structural units constituting the polymercomponent (A). It is believed that use of such a polymer component (A)improves an inhibitory ability of defects and an LWR performance of theradiation-sensitive resin composition.

Hereinafter, each component will be described.

(A) Polymer Component

The polymer component (A) has in a single polymer or different polymers,the structural unit (I) and the structural unit (II). As referred toherein, the “polymer component” may include not only one type ofpolymer, but a mixture of a plurality of types of polymers. In otherwords, the polymer component (A) may be either one type of polymerhaving the structural unit (I) and the structural unit (II), or amixture of a polymer having at least the structural unit (I) and apolymer having at least the structural unit (II). It is to be noted thatthe polymer component (A) may also include a polymer having neither theso structural unit (I) nor the structural unit (II).

The polymer component (A) may be contained in the radiation-sensitiveresin composition in, for example: (i) a form of including one type of apolymer having the structural unit (I) and the structural unit (II);(ii) a form of a mixture of a plurality of types of polymers having thestructural unit (I) and the structural unit (II); (iii) a form of amixture of a polymer having the structural unit (I) and a polymer havingthe structural unit (II); (iv) a form of both the options (i) and (iii);(v) a form of both the options (ii) and (iii); or the like. Of these,the option (i) or (ii) is preferred in light of more improvements of theinhibitory ability of defects, and the LWR performance.

The polymer component (A) satisfies the inequality (A) as describedlater. Also, the polymer component (A) satisfies the inequality (B) asdescribed later. The polymer component (A) may also have otherstructural unit than the structural unit (I) or the structural unit(II). The polymer component (A) may have each structural unit of each asingle type, or two or more types. Hereinafter, each structural unitwill be described.

Structural Unit (I)

The structural unit (I) includes a phenolic hydroxyl group. The term“phenolic hydroxyl group” as referred to herein means a hydroxy groupdirectly bonding to an aromatic ring, in general, not being limited to ahydroxy group directly bonding to a benzene ring. Due to having thestructural unit (I), the polymer component (A) is capable of enhancingthe hydrophilicity of a resist film, enables the solubility in adeveloper solution to be appropriately adjusted, and also enables theadhesiveness of a resist pattern to the substrate to be improved.Additionally, in the case of an exposure with KrF, EUV or an electronbeam, the sensitivity of the radiation-sensitive resin composition canbe more improved.

Examples of the structural unit (I) include a structural unitrepresented by the following formula (1), and the like.

In the above formula (1), R¹ represents a hydrogen atom, a fluorineatom, a methyl group or a trifluoromethyl group; R² represents a singlebond, —O—, —COO—* or —CONH—*, wherein * denotes a binding site to Ar; Arrepresents a group obtained from an arene having 6 to 20 ring atoms byremoving (p+q+1) hydrogen atoms on the aromatic ring; p is an integer of0 to 10, in a case in which p is 1, R³ represents a monovalent organicgroup having 1 to 20 carbon atoms or a halogen atom, wherein in a casein which p is no less than 2, a plurality of R³s are identical ordifferent and each represent a monovalent organic group having 1 to 20carbon atoms or a halogen atom, or at least two of the plurality of R³staken together represent a part of a ring structure having 4 to 20 ringatoms together with the carbon atom to which the at least two of theplurality of R³ bond; and q is an integer of 1 to 11, wherein (p+q) isno greater than 11.

R¹ represents, in light of the degree of copolymerization of a monomerthat gives a structural unit (I), preferably a hydrogen atom or a methylgroup, and more preferably a hydrogen atom.

R² represents preferably a single bond or —COO—*, and more preferably asingle bond.

The term number of “ring atoms” as referred to herein means the numberof atoms so constituting the ring in an alicyclic structure, an aromaticcarbocyclic structure, an aliphatic heterocyclic structure or anaromatic heterocyclic structure, and in the case of a polycyclic ringstructure, the number of “ring atoms” means the number of atomsconstituting the polycyclic ring.

Examples of the arene having 6 to 20 ring atoms that gives Ar includebenzene, naphthalene, anthracene, phenanthrene, tetracene, pyrene andthe like. Of these, benzene or naphthalene is preferred, and benzene ismore preferred.

The term “organic group” as referred to herein means a group thatincludes at least one carbon atom. The monovalent organic group having 1to 20 carbon atoms represented by R³ is exemplified by: a monovalenthydrocarbon group having 1 to 20 carbon atoms; a group that includes adivalent hetero atom-containing group between two adjacent carbon atomsor at the end of the atomic bonding side of the monovalent hydrocarbongroup having 1 to 20 carbon atoms; a group obtained by substituting apart or all of hydrogen atoms of the monovalent hetero atom-containinggroup included in the monovalent hydrocarbon group having 1 to 20 carbonatoms or the group that includes the divalent hetero atom-containinggroup; and the like.

The “hydrocarbon group” may include a chain hydrocarbon group, analicyclic hydrocarbon group and an aromatic hydrocarbon group. This“hydrocarbon group” may be a saturated hydrocarbon group or anunsaturated hydrocarbon group. The “chain hydrocarbon group” as referredto herein means a hydrocarbon group not including a ring structure butcomprising only a chain structure, and both a straight chain hydrocarbongroup and a branched hydrocarbon group may be involved. The “alicyclichydrocarbon group” as referred to herein means a hydrocarbon group notincluding an aromatic structure but comprising only an alicyclicstructure as the ring structure, and both a monocyclic alicyclichydrocarbon group and a polycyclic alicyclic hydrocarbon group may beinvolved. However, the alicyclic hydrocarbon group does not need to beconstituted with only the alicyclic structure, and a part thereof mayinclude a chain structure. The “aromatic hydrocarbon group” as referredto herein means a hydrocarbon group including an cyclic structure as thering structure. However, the aromatic hydrocarbon group does not need tobe constituted with only the cyclic structure, and a part thereof mayinclude a chain structure and/or an alicyclic structure.

The monovalent hydrocarbon group having 1 to 20 carbon atoms isexemplified by a monovalent chain hydrocarbon group having 1 to 20carbon atoms, monovalent alicyclic hydrocarbon group having 3 to 20carbon atoms, monovalent aromatic hydrocarbon group having 6 to 20carbon atoms and the like.

Examples of the monovalent chain hydrocarbon group having 1 to 20 carbonatoms include:

alkyl groups such as a methyl group, an ethyl group, a n-propyl groupand an i-propyl group;

alkenyl groups such as an ethenyl group, a propenyl group and a butenylgroup;

alkynyl groups such as an ethynyl group, a propynyl group and a butynylgroup; and the like.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 20carbon atoms include:

alicyclic saturated hydrocarbon groups such as a cyclopentyl group, acyclohexyl group, a norbornyl group, an adamantyl group, a tricyclodecylgroup and a tetracyclododecyl group;

alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group,a cyclohexenyl group, a norbornenyl group, a tricyclodecenyl group and atetracyclododecenyl group; and the like.

Examples of the monovalent aromatic hydrocarbon group having 6 to 20carbon atoms include:

aryl groups such as a phenyl group, a tolyl group, a xylyl group, anaphthyl group and an anthryl group;

aralkyl groups such as a benzyl group, a phenethyl group, a naphthylmethyl group, and an anthryl methyl group; and the like.

Examples of the hetero atom constituting the monovalent or divalenthetero atom-containing group include an oxygen atom, a nitrogen atom, asulfur atom, a phosphorus atom, a silicon atom, a halogen atom, and thelike. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom, and an iodine atom.

Examples of the divalent hetero atom-containing group include —O—, —CO—,—S—, —CS—, —NR′—, a group obtained by combining two or more of these,and the like, wherein R′ represents a hydrogen atom or a monovalenthydrocarbon group.

Examples of the monovalent hetero atom-containing group include halogenatoms such as a fluorine atom, a chlorine atom, a bromine atom and aniodine atom, a hydroxy group, a carboxy group, a cyano group, an aminogroup, a sulfanyl group, and the like.

R³ represents preferably a monovalent hydrocarbon group, and morepreferably an alkyl group.

Examples of the ring structure having 4 to 20 ring atoms representedtaken together by two or more of the plurality of R³s include: alicyclicstructures such as a cyclopentane structure, a cyclohexane structure, acyclopentene structure and a cyclohexene structure; aliphaticheterocyclic structures such as a lactone structure and a cyclic etherstructure; and the like.

In the above formula (1), p is preferably 0 to 2, more preferably 0 or1, and still more preferably 0.

In the above formula (1), q is preferably 1 to 3, and more preferably 1or 2.

Examples of the structural unit (I) include structural units representedby the following formulae (1-1) to (1-12) (hereinafter, may be alsoreferred to as “structural units (I-1) to (I-12)”), and the like.

In the above formulae (1-1) to (1-12), R¹ is as defined in the aboveformula (1).

Of these, the structural unit (I-1), (I-2), (I-6) or (I-8) is preferred.

The lower limit of the proportion of the structural unit (I) containedwith respect to the total structural units constituting the polymercomponent (A) is preferably 10 mol %, more preferably 20 mol %, andstill more preferably 30 mol %. The upper limit of the proportion of thestructural unit (I) contained is preferably 80 mol %, more preferably 70mol %, and still so more preferably 60 mol %. When the proportion of thestructural unit (I) contained falls within the above range, moreimprovements of the inhibitory ability of defects, and the LWRperformance of the radiation-sensitive resin composition are enabled.

Structural Unit (II)

The structural unit (II) includes an acid-labile group (hereinafter, maybe also referred to as “acid-labile group (a)”). The term “acid-labilegroup” as referred to herein means a group that substitutes for thehydrogen atom included in a carboxy group, a sulfo group, a phenolichydroxyl group and the like, and that will be dissociated by an actionof an acid. The acid-labile group (a) is dissociated by an action of anacid from the acid generator (B) generated upon an exposure, leading toa change in a solubility of the polymer component (A) in a developersolution, thereby enabling a resist pattern to be formed.

The structural unit (II) is exemplified by a structural unit representedby the following formula (2-1A), formula (2-1B), formula (2-1C), formula(2-2A) or formula (2-2B), and the like. —CR^(X)R^(Y)R^(Z), a group thatincludes an unsaturated alicyclic structure or —CR^(U)R^(V)(OR^(W)),which bonds to an oxy-oxygen atom derived from a carboxy group or aphenolic hydroxyl group may be the acid-labile group (a).

In the above formulae (2-1A), (2-1B), (2-1C), (2-2A) and (2-2B), R^(T)seach independently represent a hydrogen atom, a fluorine atom, a methylgroup or a trifluoromethyl group.

In the above formulae (2-1A) and (2-1B), R^(X)s each independentlyrepresent a monovalent hydrocarbon group having 1 to 20 carbon atoms;and R^(Y) and R^(Z) each independently represent a monovalenthydrocarbon group having 1 to 20 carbon atoms, or R^(Y) so and R^(Z)taken together represent a part of an alicyclic structure having 3 to 20ring atoms together with the carbon atom to which R^(Y) and R^(Z) bond.

In the formula (2-1C), R^(A) represents a hydrogen atom; R^(B) and R^(C)each independently represent a hydrogen atom or a monovalent hydrocarbongroup having 1 to 20 carbon atoms; and R^(D) represents a divalenthydrocarbon group having 1 to 20 carbon atoms that constitutes anunsaturated alicyclic structure having 4 to 20 ring atoms together withthe carbon atoms to which R^(A), R^(B) and R^(C) bond, respectively.

In the above formulae (2-2A) and (2-2B), R^(U) and R^(V) eachindependently represent a hydrogen atom or a monovalent hydrocarbongroup having 1 to 20 carbon atoms; and R^(W) represents a monovalenthydrocarbon group having 1 to 20 carbon atoms, or R^(U) and R^(V) takentogether represent a part of an alicyclic structure having 3 to 20 ringatoms together with the so carbon atom to which R^(U) and R^(V) bond, orR^(U) and R^(W) taken together represent a part of an aliphaticheterocyclic structure having 5 to 20 ring atoms together with thecarbon atom to which R^(U) bonds and with the oxygen atom to which R^(W)bonds.

R^(T) represents preferably a hydrogen atom or a methyl group in lightof the degree of copolymerization of a monomer that gives a structuralunit (II)

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atomswhich may be represented by R^(X), R^(Y), R^(Z), R^(B), R^(C), R^(U),R^(V) or R^(W) include groups similar to the hydrocarbon groupsexemplified as R³ in the above formula (1), and the like.

Examples of the divalent hydrocarbon group having 1 to 20 carbon atomsrepresented by R^(D) include groups obtained by removing one hydrogenatom from the monovalent hydrocarbon group exemplified as R³ in theabove formula (1), and the like.

R^(X) represents preferably an alkyl group or an aryl group.

R^(Y) and R^(Z) each represent preferably an alkyl group or an alicyclicsaturated hydrocarbon group.

Examples of the alicyclic structure having 3 to 20 ring atomsrepresented taken together by R^(Y) and R^(Z) or R^(U) and R^(V)include:

saturated alicyclic structures such as a cyclopropane structure, acyclobutane structure, a cyclopentane structure, a cyclohexanestructure, a norbornane structure and an adamantane structure;

unsaturated alicyclic structures such as a cyclopropene structure, acyclobutene structure, a cyclopentene structure, a cyclohexene structureand a norbornene structure; and the like.

Of these, a cyclopentane structure, a cyclohexane structure, acyclohexene structure or an adamantane structure is preferred.

Examples of the unsaturated alicyclic structure having 4 to 20 ringatoms represented by R^(D) together with the carbon atoms to whichR^(A), R^(B) and R^(C) bond, respectively, include unsaturated alicyclicstructures such as a cyclobutene structure, a cyclopentene structure, acyclohexene structure and a norbornene structure, and the like.

Examples of the aliphatic heterocyclic structure having 5 to 20 ringatoms represented by R^(U) and R^(W) taken together include: saturatedoxygen-containing heterocyclic structures such as an oxacyclobutanestructure, an oxacyclopentane structure and an oxacyclohexane structure;unsaturated oxygen-containing heterocyclic structures such as anoxacyclobutene structure, an oxacyclopentene structure and anoxacyclohexene structure; and the like.

The structural unit represented by the above formula (2-1A) ispreferably a structural unit derived from 1-alkylcycloalkan-1-yl(meth)acrylate, a structural unit derived from 1-arylcycloalkan-1-yl(meth)acrylate, or a structural unit derived from 2-adamantylpropan-2-yl(meth)acrylate. The structural unit represented by the above formula(2-1B) is preferably a structural unit derived from t-alkyloxystyrene.The structural unit represented by the above formula (2-1C) ispreferably a structural unit derived from cyclohexen-3-yl(meth)acrylate. The structural unit represented by the above formula(2-2A) is preferably (1-ethoxy)ethoxy (meth)acrylate. The structuralunit represented by the above formula (2-2B) is preferablyp-(1-ethoxy)ethoxystyrene.

The structural unit (II) is preferably the structural unit representedby the above formula (2-1A), (2-1B) or (2-1C).

The lower limit of the proportion of the structural unit (II) containedwith respect to the total structural units constituting the polymercomponent (A) is preferably 5 mol %, more preferably 10 mol %, stillmore preferably 15 mol %, and particularly preferably 20 mol %. Theupper limit of the proportion of the structural unit (II) contained ispreferably 90 mol %, more preferably 80 mol %, still more preferably 70mol %, and particularly preferably 65 mol %. When the proportion of thestructural unit (II) contained falls within the above range, thesensitivity of the radiation-sensitive composition can be more enhanced,thereby consequently enabling the inhibitory ability of defects, and theLWR performance to be more improved.

Other Structural Unit

The polymer component (A) may have in a single polymer or differentpolymers, other structural unit than the structural unit (I) or thestructural unit (II). The other structural unit is exemplified by: astructural unit (hereinafter, may be also referred to as “structuralunit (III)”) that includes a lactone structure, a cyclic carbonatestructure, a sultone structure or a combination thereof; a structuralunit (hereinafter, may be also referred to as “structural unit (IV)”)that includes an alcoholic hydroxy group other than the structural unit(III); a structural unit (hereinafter, may be also referred to as“structural unit (V)”) that includes an acid-nonlabile hydrocarbongroup; and the like.

It is preferred that the polymer component (A) has the other structuralunit. The radiation-sensitive resin composition in which the polymercomponent (A) has the other structural unit tends to lead to theinhibitory ability of defects, and the LWR performance being moreimproved. Hereinafter, the structural units (III) to (V) will bedescribed.

Structural unit (III)

The structural unit (III) includes a lactone structure, a cycliccarbonate structure, a sultone structure or a combination thereof. Whenthe polymer component (A) has the o structural unit (III), solubility ina developer solution can be improved and consequently, the inhibitoryability of defects, and the LWR performance of the radiation-sensitivecomposition can be more improved. In addition, the adhesiveness of theresist pattern with the substrate can be more improved.

Examples of the structural unit (III) include structural unitsrepresented by the following formulae, and the like.

In the above formulae, R^(L1) represents a hydrogen atom, a fluorineatom, a methyl group or a trifluoromethyl group.

The structural unit (III) is preferably a structural unit that includesa lactone structure, more preferably a structural unit that includes anorbornanelactone structure, and still more preferably a structural unitderived from cyanonorbornanelactone-yl (meth)acrylate.

In a case in which the polymer component (A) has the structural unit(III), the upper limit of the proportion of the structural unit (III)contained with respect to total structural units constituting thepolymer component is preferably 60 mol %, more preferably 50 mol %, andstill more preferably 30 mol %. The lower limit of the proportion of thestructural unit (III) is, for example, 1 mol %.

Structural Unit (IV)

The structural unit (IV) includes an alcoholic hydroxy group other thanthe structural unit (III). When the polymer component (A) has thestructural unit (IV), solubility in a developer solution can be improvedand consequently, the inhibitory ability of defects, and the LWRperformance of the radiation-sensitive composition can be more improved.

Examples of the structural unit (IV) include: structural units thatinclude a hydroxychain hydrocarbon group or a hydroxyalicyclichydrocarbon group such as a structural unit derived from3-hydroxyadamantan-1-yl (meth)acrylate; a structural unit derived from2-hydroxyethyl (meth)acrylate; structural units that include ahydroxyfluorinated alkyl group such as a structural unit derived from2-hydroxy-2-trifluoromethyl-1,1,1-trifluoropropan-1-ylnorbornane-yl(meth)acrylate; and the like.

In a case in which the polymer component (A) has the structural unit(IV), the upper limit of the proportion of the structural unit (IV)contained with respect to total structural units constituting thepolymer component is preferably 60 mol %, and more preferably 50 mol %.The lower limit of the proportion of the structural unit (IV) is, forexample, 1 mol %.

Structural Unit (V)

The structural unit (V) includes an acid-nonlabile hydrocarbon group.When the polymer component (A) has the structural unit (V), solubilityin a developer solution can be improved and consequently, the inhibitoryability of defects, and the LWR performance of the radiation-sensitivecomposition can be more improved.

Examples of a monomer that gives a structural unit (V) include styrene,vinylnaphthalene, phenyl (meth)acrylate, benzyl (meth)acrylate, n-pentyl(meth)acrylate, cyclohexyl (meth)acrylate,spiro[tetrahydronaphthalene-1,5′-methylenebutyrolactone], and the like.

In a case in which the polymer component (A) has the structural unit(V), the upper limit of the proportion of the structural unit (V)contained with respect to the total structural units constituting thepolymer component (A) is preferably 60 mol %, and more preferably 50 mol%. The lower limit of the proportion of the structural unit (V) is, forexample, 1 mol %.

The lower limit of polystyrene equivalent weight-average molecularweight (Mw) of the polymer component (A) as determined by gel permeationchromatography (GPC) is preferably 2,000, more preferably 3,000, stillmore preferably 4,000, and particularly preferably 5,000. The upperlimit of the Mw is preferably 50,000, more preferably 30,000, still morepreferably 15,000, and particularly preferably 8,000. When the Mw of thepolymer component (A) falls within the above range, coatingcharacteristics of the radiation-sensitive resin composition can be moreimproved.

The lower limit of the dispersity index, i.e., a ratio of thepolystyrene-equivalent number-average molecular weight (Mn) to Mw(Mw/Mn) as determined by GPC, of the polymer component (A) is preferably1.1, more preferably 1.25, still more preferably 1.4, and particularlypreferably 1.5. The upper limit of the dispersity index is preferably 5,more preferably 3, and still more preferably 2. When the Mw/Mn of thepolymer component (A) falls within the above range, more improvements ofthe inhibitory ability of defects, and the LWR performance of theradiation-sensitive resin composition are enabled.

Mw and Mn of the polymer component referred to herein are determined byusing gel permeation chromatography (GPC) under the followingconditions.

GPC columns: “G2000 HXL” x 2, “G3000 HXL” x 1, and “G4000 HXL” x 1,available from Tosoh Corporation;

flow rate: 1.0 mL/min;

elution solvent: tetrahydrofuran;

sample concentration: 1.0% by mass;

amount of injected sample: 100 μL;

column temperature: 40° C.;

detector: differential refractometer; and

standard substance: mono-dispersed polystyrene

Inequality (A)

The polymer component (A) satisfies the following inequality (A).

X1<X2   (A)

In the above inequality (A), X1 represents a proportion (mol %) of thestructural unit (I) included with respect to total structural unitsconstituting the polymer component (A) included in a fraction(hereinafter, may be also referred to as “fraction A”) eluted until aretention time at which a cumulative area accounts for 1% of a totalarea on a gel permeation chromatography (GPC) elution curve of thepolymer component (A) detected by a differential refractometer; and X2represents a proportion (mol %) of the structural unit (I) included withrespect to total structural units constituting the polymer component(A).

X1 (mol %) may be determined by, for example, preparatively collectingthe fraction A that corresponds to an area accounting for 1% from ashorter retention time in preparative GPC performed under the followingconditions (see, FIG. 1), and then measuring the proportion of thepolymer component contained in the fraction A thus collectedpreparatively, with respect to the total structural units constitutingthe structural unit (I). It is to be noted that in the preparative GPC,since higher-molecular weight components are preparatively collectedmore earlily, a fraction of shorter retention time relatively includeshigher-molecular weight components in a larger amount as compared with afraction of a so longer retention time. In a case in which the polymercomponent (A) is contained in a composition, X1 may be determined bypreparatively collecting the polymer component (A) from the composition,and then subjecting the resultant polymer component (A) to preparativeGPC in a similar manner to that described above.

preparative GPC columns: “JAIGEL 2.5H+2H” available from JapanAnalytical Industry Co., Ltd.;

flow rate: 4.0 mL/min;

elution solvent: tetrahydrofuran;

sample concentration: 3% by mass;

amount of injected sample: 3 mL;

column temperature: 40° C.; and

detector: differential refractometer

The proportion of the structural unit (I) contained in the polymercomponent may be determined by using, for example, PyGC-MS (AgilentTechnologies, Inc., etc.) to calculate an area ratio of each monomerthat gives each structural unit, and then summing up the area ratios forthe monomer that gives a structural unit (I), among the area ratios ofrespective monomers.

X2 (mol %) may be determined by using, for example, PyGC-MS to measurethe proportion of the structural unit (I) contained with respect to thetotal structural units constituting the polymer component, on theentirety of the polymer component (A) with out performing thepreparative collection. The proportion of the structural unit (I)contained may be determined in a similar manner to that described above.

Accordingly, with respect to the proportion (mol %) of the structuralunit (I) in the polymer component (A), the proportion (X1) with respectto the total area, falling under a high-molecular weight region of theaccumulative area accounting for 1% from the higher-molecular weightside on a gel permeation chromatography elution curve detected by adifferential refractometer is less than the proportion (X2) in theentirety of the polymer component (A).

The lower limit of X1 is preferably 25 mol %, more preferably 30 mol %,and still more preferably 35 mol %. The upper limit of X1 is preferably60 mol %, more preferably 50 mol %, and still more preferably 45 mol %.

The lower limit of (X2−X1) obtained by subtract X1 from X2 is preferably0.1 mol %, more preferably 1 mol %, and still more preferably 1.5 mol %.The upper limit of (X2−X1) is preferably 10 mol %, and more preferably 6mol %.

Inequality (B)

The polymer component (A) satisfies the following inequality (B).

$\begin{matrix}{\frac{X\; 2}{X\; 1} > 1.0} & (B)\end{matrix}$

In the above inequality (B), X1 and X2 are as defined in the aboveinequality (A).

The lower limit of a ratio (X2/X1) of X2 to X1 in the above inequality(B) is preferably 1.01, more preferably 1.03, and still more preferably1.05. The upper limit of X2/X1 is preferably 1.20, and more preferably1.15.

The lower limit of the molecular weight of a high-molecular weightregion of the accumulative area accounting for 1% from thehigher-molecular weight side on a gel permeation chromatography elutioncurve detected by a differential refractometer in the polymer component(A) is preferably 3,000, and more preferably 5,000. The upper limit ofthe molecular weight is preferably 15,000, and more preferably 10,000.

The lower limit of the proportion of the polymer component (A) containedin the radiation-sensitive resin composition with respect to the totalcomponents other than the solvent (D) is preferably 50% by mass, morepreferably 60% by mass, and still more preferably 70% by mass.

Synthesis Procedure of Polymer Component (A)

The polymer component (A) may be synthesized by mixing monomers thateach give the structural unit (I), the structural unit (II) and asneeded other structural unit in an appropriate molar ratio, andpolymerizing by a well-known process in the presence of a polymerizationinitiator such as azobisisobutyronitrile (AIBN), and in the presence ofor absence of a chain transfer agent such as 2-cyano-2-propyl dodecyltrithiocarbonate. In a case in which the structural unit (I) is astructural unit derived from hydroxystyrene, hydroxyvinylnaphthalene orthe like, these structural units may be formed by, for example, usingacetoxy styrene, acetoxy vinylnaphthalene or the like as the monomer toobtain a polymer component, and hydrolyzing the polymer component in thepresence of base such as triethylamine. The polymer component (A) may beobtained by mixing a plurality of types of polymers each having thestructural unit (I), the structural unit (II) and as needed otherstructural unit synthesized by the process described above, or thepolymer component (A) may be also obtained by mixing a polymer havingthe structural unit (I) and as needed other structural unit, and apolymer having the structural unit (II) and as needed other structuralunit. Furthermore, the polymer component (A) may be also obtained bypreparatively collecting using preparative GPC or the like, appropriateportions of the polymer components each having the structural unit (I),the structural unit (II) and as needed the other structural unit whichhad been synthesized by the aforementioned well-known process.

The polymer component (A) may be obtained by synthesizing through thepolymerization by the well-known process described above, and thenpurifying the resulting polymer component by a well-known procedure. Thepurification procedure is exemplified by: purification with a solvent,purification through preparative GPC, and the like. Exemplarypurification with a solvent includes, for example, adding butyl acetateto dissolve the solid; washing with an aqueous sodium bicarbonatesolution; then washing an organic layer with ultra pure water; and thenadding a resultant concentrate into hexane to allow coagulation of thepolymer, and the like. The purification through preparative GPCincludes, for example, using the preparative GPC to remove: a fractioncorresponding to a cumulative area accounting for 25% of a total area onthe GPC elution curve from a shorter retention time; and a fractioncorresponding to a cumulative area accounting for 25% of a total area onthe GPC elution curve from a longer retention time, whereby a remainderfraction (a fraction corresponding to a cumulative area accounting for25% to 75% of the total area on the GPC elution area) is preparativelycollected, which is employed as the polymer component (A), and the like.

(B) Acid Generator

The acid generator (B) is a substance that generates an acid(hereinafter, may be also referred to as “acid (b)”) upon irradiationwith a radioactive ray. Examples of the radioactive ray include:electromagnetic waves such as visible light rays, ultraviolet rays, farultraviolet rays, EUV, X-rays and γ-rays; electron beams, chargedparticle rays such as a-rays, and the like. The acid (b) generated fromthe acid generator (B) allows the acid-labile group (a) included in thepolymer component (A) to be dissociated, thereby generating a carboxygroup, a sulfo group, a phenolic hydroxyl group, etc. As a result, thesolubility of the polymer component (A) in the developer solutionchanges, and thus formation of a resist pattern from theradiation-sensitive resin composition is enabled. The acid generator (B)may be contained in the radiation-sensitive resin composition either inthe form of a low-molecular-weight compound (hereinafter, may be alsoreferred to as “(B) acid generating agent” or “acid generating agent(B)”) or in the form of an acid generator so incorporated as a part ofthe polymer such as the polymer component (A), or may be in both ofthese forms.

The lower limit of the temperature at which the acid (b) allows theacid-labile group (a) to be dissociated is preferably 80° C., morepreferably 90° C., and still more preferably 100° C. The upper limit ofthe temperature is preferably 130° C., more preferably 120° C., andstill more preferably 110° C. The lower limit of the time period forallowing the acid-labile group (a) to be dissociated by the acid (b) ispreferably 10 sec, and more preferably 1 min. The upper limit of thetime period is preferably 10 min, and more preferably 2 min.

The acid generated from the acid generator (B) is exemplified by asulfonic acid, an imidic acid, and the like.

The acid generating agent (B) is exemplified by an onium salt compound,an N-sulfonyloxyimide compound, a sulfonimide compound, ahalogen-containing compound, a diazo ketone compound, and the like.

Exemplary onium salt compound includes a sulfonium salt, atetrahydrothiophenium salt, an iodonium salt, a phosphonium salt, adiazonium salt, a pyridinium salt, and the like.

Specific examples of the acid generating agent (B) include compoundsdisclosed in paragraphs [0080] to [0113] of Japanese Unexamined PatentApplication, Publication No. 2009-134088, and the like.

The acid generating agent (B) that generates sulfonic acid uponirradiation with a radioactive ray acid is exemplified by a compoundrepresented by the following formula (3) (hereinafter, may be alsoreferred to as “compound (3)”), and the like. When the acid generatingagent (B) has the following structure, it is expected that a diffusionlength of the acid (b) generated in the resist film will be moreproperly reduced through e.g., an interaction with the structural unit(I) of the polymer component (A), or the like, and as a result, moreimprovements of the inhibitory ability of defects, and the LWRperformance of the radiation-sensitive resin composition are enabled.

In the above formula (3), R^(p1) represents a monovalent group thatincludes a ring structure having 5 or more ring atoms; R^(p2) representsa divalent linking group; R^(p3) and R^(p4) each independently representa hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having1 to 20 carbon atoms or a monovalent fluorinated hydrocarbon grouphaving 1 to 20 carbon atoms; R^(p5) and R^(p6) each independentlyrepresent a fluorine atom or a monovalent fluorinated hydrocarbon grouphaving 1 to 20 carbon atoms; n^(p1) is an integer of 0 to 10; n^(p2) isan integer of 0 to 10; n^(p3) is an integer of 0 to 10, wherein the sumof n^(p1), n^(p2) and n^(p3) is no less than 1 and no greater than 30,and wherein in a case in which n^(p1) is no less than 2, a plurality ofR^(p2)s are each identical or different, in a case in which n^(p2) is noless than 2, a plurality of R^(p3)s are each identical or different anda plurality of R^(p4)s are each identical or different, and in a case inwhich n^(p3) is no less than 2, a plurality of R^(p3)s are eachidentical or different and a plurality of R^(p6)s are each identical ordifferent; and T⁺ represents a radiation-sensitive monovalent oniumcation.

The monovalent group that includes a ring structure having 5 or morering atoms which is represented by R^(p1) is exemplified by: amonovalent group that includes an alicyclic structure having 5 or morering atoms; a monovalent group that includes an aliphatic heterocyclicstructure having 5 or more ring atoms; a monovalent group that includesan cyclic structure having 5 or more ring atoms; a monovalent group thatincludes an aromatic heterocyclic structure having 5 or more ring atoms;and the like.

Examples of the alicyclic structure having 5 or more ring atoms include:

monocyclic saturated alicyclic structures such as a cyclopentanestructure, a cyclohexane structure, a cycloheptane structure, acyclooctane structure, a cyclononane structure, a cyclodecane structureand a cyclododecane structure;

monocyclic unsaturated alicyclic structures such as a cyclopentenestructure, a cyclohexene structure, a cycloheptene structure, acyclooctene structure and a cyclodecene structure;

polycyclic saturated alicyclic structures such as a norbornanestructure, an adamantane structure, a tricyclodecane structure and atetracyclododecane structure;

polycyclic unsaturated alicyclic structures such as a norbornenestructure and a tricyclodecene structure; and the like.

Examples of the aliphatic heterocyclic structure having 5 or more ringatoms include:

lactone structures such as a hexanolactone structure and anorbornanelactone structure;

sultone structures such as a hexanosultone structure and anorbornanesultone structure;

oxygen atom-containing heterocyclic structures such as anoxacycloheptane structure and an oxanorbornane structure;

nitrogen atom-containing heterocyclic structures such as anazacyclohexane structure and a diazabicyclooctane structure;

sulfur atom-containing heterocyclic structures such as a thiacyclohexanestructure and a thianorbornane structure; and the like.

Examples of the cyclic structure having 5 or more ring atoms include abenzene structure, a naphthalene structure, a phenanthrene structure, ananthracene structure, and the like.

Examples of the aromatic heterocyclic structure having 5 or more ringatoms include:

oxygen atom-containing heterocyclic structures such as a furanstructure, a pyran structure, a benzofuran structure and a benzopyranstructure;

nitrogen atom-containing heterocyclic structures such as a pyridinestructure, a pyrimidine structure and an indole structure; and the like.

The lower limit of the number of ring atoms of the ring structureincluded in R^(p1) is preferably 6, more preferably 8, still morepreferably 9, and particularly preferably 10. The upper limit of thenumber of ring atoms is preferably 15, more preferably 14, still morepreferably 13, and particularly preferably 12. When the number of ringatoms falls within the above range, the aforementioned diffusion lengthof the acid may be further properly reduced, and as a result, moreimprovements of the LWR performances, etc., of the radiation-sensitiveresin composition are enabled.

A part or all of hydrogen atoms included in the ring structure of R^(p1)may be substituted with a substituent. Examples of the substituentinclude halogen atoms such as a fluorine atom, a chlorine atom, abromine atom and an iodine atom, a hydroxy group, a carboxy group, acyano group, a nitro group, an alkoxy group, an alkoxycarbonyl group, analkoxycarbonyloxy group, an acyl group, an acyloxy group, and the like.Of these, the hydroxy group is preferred.

R^(p1) represents preferably a monovalent group that includes analicyclic structure having 5 or more ring atoms or a monovalent groupthat includes an aliphatic heterocyclic structure having 5 or more ringatoms, more preferably a monovalent group that includes an alicyclicstructure having 9 or more ring atoms or a monovalent group thatincludes an aliphatic heterocyclic structure having 9 or more ringatoms, still more preferably an adamantyl group, a hydroxyadamantylgroup, a norbornanelactone-yl group, a norbornanesultone-yl group or a5-oxo-4-oxatricyclo[4.3.1.1^(3,8)]undecan-yl group, and particularlypreferably an adamantyl group.

Examples of the divalent linking group represented by R^(p2) include acarbonyl group, an ether group, a carbonyloxy group, a sulfide group, athiocarbonyl group, a sulfonyl group, a divalent hydrocarbon group, andthe like. Of these, the carbonyloxy group, the sulfonyl group, analkanediyl group or a divalent alicyclic saturated hydrocarbon group ispreferred, the carbonyloxy group or the divalent alicyclic saturatedhydrocarbon group is more preferred, the carbonyloxy group or anorbornanediyl group is still more preferred, and the carbonyloxy groupis particularly preferred. It is to be noted that in a case in whichR^(p2) represents the carbonyloxy group, orientation of the carbonyloxygroup is not particularly limited. More specifically, a carbonyl carbonatom of the carbonyloxy group may bond to R^(p1), or an oxy-oxygen atommay bond to R^(p1).

The monovalent hydrocarbon group having 1 to 20 carbon atoms which maybe represented by R^(p3) or R^(p4) is exemplified by an alkyl grouphaving 1 to 20 carbon atoms, and the like. The monovalent fluorinatedhydrocarbon group having 1 to 20 carbon atoms which may be representedby R^(p3) or R^(p4) is exemplified by a fluorinated alkyl group having 1to 20 carbon atoms, and the like. R^(p3) and R^(p4) each independentlyrepresent preferably a hydrogen atom, a fluorine atom or a fluorinatedalkyl group, more preferably a fluorine atom or a perfluoroalkyl group,and still more preferably a fluorine atom or a trifluoromethyl group.

The monovalent fluorinated hydrocarbon group having 1 to 20 carbon atomswhich may be represented by R^(p5) or R^(p6) is exemplified by afluorinated alkyl group having 1 to 20 so carbon atoms, and the like.R^(p5) and R^(p6) each independently represent preferably a fluorineatom or a fluorinated alkyl group, more preferably a fluorine atom or aperfluoroalkyl group, still more preferably a fluorine atom or atrifluoromethyl group, and particularly preferably a fluorine atom.

In the above formula (3), n^(p1) is preferably 0 to 5, more preferably 0to 3, still more preferably 0 to 2, and particularly preferably 0 or 1.

In the above formula (3), n^(p2) is preferably 0 to 5, more preferably 0to 2, still more preferably 0 or 1, and particularly preferably 0.

The lower limit of n^(p3) is preferably 1, and more preferably 2. Whenn^(p3) is no less than 1, the strength of the acid generated from thecompound (3) may be increased, and consequently the inhibitory abilityof defects, and the LWR performance of the radiation-sensitive resincomposition may be more improved. The upper limit of n^(p3) ispreferably 4, more preferably 3, and still more preferably 2.

The lower limit of the sum of n^(p1), n^(p2) and n^(p3), i.e.,(n_(p1)+n^(p2)+n^(p3)), is preferably 2, and more preferably 4. Theupper limit of the sum of n^(p1), n^(p2) and n^(p3) is preferably 20,and more preferably 10.

Examples of the radiation-sensitive monovalent onium cation representedby T⁺ include a cation represented by the following formula (r-a)(hereinafter, may be also referred to as “cation (r-a)”), a cationrepresented by the following formula (r-b) (hereinafter, may be alsoreferred to as “cation (r-b)”), a cation represented by the followingformula (r-c) (hereinafter, may be also referred to as “cation (r-c)”),and the like.

In the above formula (r-a), R^(B3) and R^(B4) each independentlyrepresent a monovalent organic group having 1 to 20 carbon atoms; b3 isan integer of 0 to 11, wherein in a case where b3 is 1, R^(B5)represents a monovalent organic group having 1 to 20 carbon atoms, ahydroxy group, a nitro group or a halogen atom, in a case where b3 is noless than 2, a plurality of R^(B5)s are each identical or different, andrepresent a monovalent organic group having 1 to 20 carbon atoms, ahydroxy group, a nitro group or a halogen atom, or the plurality ofR^(B5)s taken together represent a part of a ring structure having 4 to20 ring atoms together with the carbon chain to which the plurality ofR^(B5)s bond; and n_(bb) is an integer of 0 to 3.

The monovalent organic group having 1 to 20 carbon atoms which may berepresented by R^(B3), R^(B4) or R^(B5) is exemplified by a monovalenthydrocarbon group having 1 to 20 carbon atoms, a monovalent group (g)that includes a divalent hetero atom-containing group between twoadjacent carbon atoms or at the end of the atomic bonding side of the somonovalent hydrocarbon group; a monovalent group obtained from themonovalent hydrocarbon group or the group (g) by substituting with ahetero atom-containing group a part or all of hydrogen atoms includedtherein; or the like.

R^(B3) and R^(B4) each represent preferably a monovalent unsubstitutedhydrocarbon group having 1 to 20 carbon atoms or a hydrocarbon groupobtained therefrom by substituting a hydrogen atom included therein witha substituent, more preferably a monovalent unsubstituted aromatichydrocarbon group having 6 to 18 carbon atoms or an aromatic hydrocarbongroup obtained therefrom by substituting a hydrogen atom includedtherein with a substituent, still more preferably a substituted orunsubstituted phenyl group, and particularly preferably an unsubstitutedphenyl group.

The substituent which may substitute for the hydrogen atom included inthe monovalent hydrocarbon group having 1 to 20 carbon atoms which maybe represented by R^(B3) or R^(B4) is preferably a substituted orunsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms,—OSO₂—R^(k), —SO₂—R^(k), —OR^(k), —COOR^(k), —O—CO—R^(k),—O—R^(kk)—COOR^(k), —R^(kk)—CO—R^(k) or —S—R^(k), wherein R^(k)represents a monovalent hydrocarbon group having 1 to 10 carbon atoms;and R^(kk) represents a single bond or a divalent hydrocarbon grouphaving 1 to 10 carbon atoms.

R^(B5) represents preferably a substituted or unsubstituted monovalenthydrocarbon group having 1 to 20 carbon atoms, —OSO₂—R^(k), —SO₂—R^(k),—OR^(k), —COOR^(k), —O—CO—R^(k), —O—R^(kk)—COOR^(k), —R^(kk)—CO—R^(k) or—S—R^(k), wherein R^(k) represents a monovalent hydrocarbon group having1 to 10 carbon atoms; and R^(kk) represents a single bond or a divalenthydrocarbon group having 1 to 10 carbon atoms.

In the above formula (r-b), b4 is an integer of 0 to 9; wherein in acase in which b4 is 1, R^(B6) represents a monovalent organic grouphaving 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogenatom, and in a case in which b4 is no less than 2, a plurality ofR^(B6)s are each identical or different and represent a monovalentorganic group having 1 to 20 carbon atoms, a hydroxy group, a nitrogroup or a halogen atom, or the plurality of R^(B6)s taken togetherrepresent a part of a ring structure having 4 to 20 ring atoms togetherwith the carbon chain to which the plurality of R^(B6)s bond; b5 is aninteger of 0 to 10, wherein in a case in which b5 is 1, R^(B7)represents a monovalent organic group having 1 to 20 carbon atoms, ahydroxy group, a nitro group or a halogen atom, and in a case in whichb5 is no less than 2, a plurality of R^(B7)s are each identical ordifferent and represent a monovalent organic group having 1 to 20 carbonatoms, a hydroxy group, a nitro group or a halogen atom, or theplurality of R^(B7)s taken together represent a part of a ring structurehaving 3 to 20 ring atoms taken together with the carbon atom or carbonchain to which the plurality of R^(B7)s bond; n_(b2) is an integer of 0to 3; R^(B8) represents a single bond or a divalent organic group having1 to 20 carbon atoms; and n_(b1) is an integer of 0 to 2.

R^(B6) and R^(B7) each represent preferably a substituted orunsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms,—OR^(k), —COOR^(k), —O—CO—R^(k), —O—R^(kk)—COOR^(k) or —R^(kk)—CO—R^(k),wherein R^(k) represents a monovalent hydrocarbon group having 1 to 10carbon atoms; and R^(kk) represents a single bond or a divalenthydrocarbon group having 1 to 10 carbon atoms.

In the above formula (r-c), b6 is an integer of 0 to 5, wherein in acase in which b6 is 1, R^(B9) represents a monovalent organic grouphaving 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogenatom, in a case in which b6 is no less than 2, a plurality of R^(B9)sare each identical or different and represent a monovalent organic grouphaving 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogenatom, or the plurality of R^(B9)s taken together represent a part of aring structure having 4 to 20 ring atoms together with the carbon chainto which the plurality of R^(B9)s bond; and b7 is an integer of 0 to 5,wherein in a case in which b7 is 1, R^(B10) represents a monovalentorganic group having 1 to 20 carbon atoms, a so hydroxy group, a nitrogroup or a halogen atom, and in a case in which b7 is no less than 2, aplurality of R^(B10)s are each identical or different and represent amonovalent organic group having 1 to 20 carbon atoms, a hydroxy group, anitro group or a halogen atom, or the plurality of R^(B10)s takentogether represent a part of a ring structure having 4 to 20 ring atomstogether with the carbon chain to which the plurality of R^(B10)s bond.

R^(B9) and R^(B10) each represent preferably a substituted orunsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms,—OSO₂—R^(k), —SO₂—R^(k), —OR^(k), —COOR^(k), —O—CO—R^(k),—O—R^(kk)—COOR^(k), —R^(kk)—CO—R^(k), —S—R^(k), or a ring structuretaken together represented by at least two of R^(a7) and R^(a8), whereinR^(k) represents a monovalent hydrocarbon group having 1 to 10 carbonatoms; and R^(kk) represents a single bond or a divalent hydrocarbongroup having 1 to 10 carbon atoms.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atomswhich may be represented by R^(B5), R^(B6), R^(B7), R^(B9) or R^(B10)include:

linear alkyl groups such as a methyl group, an ethyl group, a n-propylgroup and a n-butyl group;

branched alkyl groups such as an i-propyl group, an i-butyl group, asec-butyl group and a t-butyl group;

aryl groups such as a phenyl group, a tolyl group, a xylyl group, amesityl group and a naphthyl group;

aralkyl groups such as a benzyl group and a phenethyl group; and thelike.

Examples of the divalent organic group which may be represented byR^(B8) include groups obtained by removing one hydrogen atom from themonovalent organic group having 1 to 20 carbon atoms exemplified inconnection with R^(B3), R^(B4) or R^(B5) in the above formula (r-a), andthe like.

Examples of the substituent which may substitute for the hydrogen atomincluded in the hydrocarbon group which may be represented by R^(B5),R^(B6), R^(B7), R^(B9) or R^(B10) include halogen atoms such as afluorine atom, a chlorine atom, a bromine atom and an iodine atom, ahydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxygroup, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acylgroup, an acyloxy group, and the like. Of these, the halogen atom ispreferred, and a fluorine atom is more preferred.

R^(B5), R^(B6), R^(B7), R^(B9) and R^(B10) each represent preferably anunsubstituted linear or branched monovalent alkyl group, a monovalentfluorinated alkyl group, an unsubstituted monovalent aromatichydrocarbon group, —OSO₂—R^(k) or —SO₂—R^(k), more preferably afluorinated alkyl group or an unsubstituted monovalent aromatichydrocarbon group, and still more preferably a fluorinated alkyl group.

In the formula (r-a), b3 is preferably 0 to 2, more preferably 0 or 1,and still more preferably 0; and n_(bb) is preferably 0 or 1, and morepreferably 0. In the formula (r-b), b4 is preferably 0 to 2, morepreferably 0 or 1, and still more preferably 0; b5 is preferably 0 to 2,more preferably 0 or 1, and still more preferably 0; n_(b2) ispreferably 2 or 3, and more preferably 2; and n_(b1) is preferably 0 or1, and more preferably 0. In the formula (r-c), b6 and b7 are preferably0 to 2, more preferably 0 or 1, and still more preferably 0.

Of these, T⁺ represents preferably the cation (r-a), and more preferablya triphenylsulfonium cation.

Examples of the acid generating agent (B) include: as the acidgenerating agent that generates sulfonic acid, compounds represented bythe following formulae (3-1) to (3-20) (hereinafter, may be alsoreferred to as “compounds (3-1) to (3-20)”); as the acid generatingagent that generates imidic acid, compounds represented by the followingformulae (4-1) to (4-3) (hereinafter, may be also referred to as“compounds (4-1) to (4-3)”); and the like.

In the above formulae (3-1) to (3-20) and (4-1) to (4-3), T represents aradiation-sensitive monovalent onium cation.

Furthermore, the acid generator (B) is exemplified by a polymer in whicha structure of the acid generator is incorporated as a part of thepolymer component (A), such as a polymer having a structural unitrepresented by the following formula (3′).

In the above formula (3′), R^(p7) represents a hydrogen atom or a methylgroup; L⁴ represents a single bond, —COO— or a divalentcarbonyloxyhydrocarbon group; R^(p8) represents a fluorinated alkanediylgroup having 1 to 10 carbon atoms; and T⁺ represents aradiation-sensitive monovalent onium cation. It is to be noted that in acase in which L⁴ represents —COO— or a divalent carbonyloxyhydrocarbongroup, the carbonyl carbon atom of such a group bonds to the carbon atomto which R^(p7) bonds.

In light of a degree of copolymerization of a monomer that gives thestructural unit represented by the above formula (3′), R^(p7) representspreferably a methyl group.

L⁴ represents preferably a divalent carbonyloxyhydrocarbon group, andmore preferably a carbonyloxyalkanediyl group or acarbonyloxyalkanediylarenediyl group.

R^(p8) represents preferably a fluorinated alkanediyl group having 1 to4 carbon atoms, more preferably a perfluoroalkanediyl group having 1 to4 carbon atoms, and still more preferably a hexafluoropropanediyl group.

The acid generating agent (B) is preferably the compound (3), and morepreferably the compound (3-2), (3-11), (3-12), (3-13), (3-15) or (3-20).

In a case in which the acid generator (B) is the acid generating agent(B), the lower limit of the content of the acid generating agent (B)with respect to 100 parts by mass of the polymer component (A) ispreferably 0.1 parts by mass, more preferably 1 part by mass, still morepreferably 5 parts by mass, and particularly preferably 10 parts bymass. The upper limit of the content of the acid generating agent (B) ispreferably 50 parts by mass, more preferably 40 parts by mass, stillmore preferably 30 parts by mass, and particularly preferably 25 partsby mass. When the content of the acid generating agent (B) falls withinthe above range, sensitivity and developability the radiation-sensitiveresin composition may be improved, and consequently the inhibitoryability of defects, and the LWR performance can be more improved. One,or two or more types of the acid generator (B) may be contained.

(C) Acid Diffusion Controller

The acid diffusion controller (C) controls a phenomenon of diffusion ofthe acid, which was generated from the acid generator (B), etc. upon theexposure, in the resist film, whereby the effect of inhibiting unwantedchemical reactions in an unexposed region is exhibited. In addition, thestorage stability of the radiation-sensitive resin composition isimproved and the resolution thereof as a resist is more improved.Moreover, variation of the line width of the resist pattern caused byvariation of post-exposure time delay from the exposure until adevelopment treatment can be suppressed, which enables theradiation-sensitive resin composition with superior process stability tobe obtained. The acid diffusion controller (C) may be contained in theradiation-sensitive resin composition in the form of a low-molecularweight compound (hereinafter, may be also referred to as “(C) aciddiffusion control agent” or “acid diffusion control agent (C)” asappropriate) or in the form incorporated as a part of the polymer, ormay be in both of these forms.

The acid diffusion control agent (C) is exemplified by a nitrogenatom-containing compound, a photolabile base that generates a weak acidthrough photosensitization upon an exposure, and the like.

Examples of the nitrogen atom-containing compound include: aminecompounds such as tripentylamine and trioctylamine; amidegroup-containing compounds such as formamide and N,N-dimethylacetamide;urea compounds such as urea and 1,1-dimethylurea; nitrogen-containingheterocyclic compounds such as pyridine,N-(undecylcarbonyloxyethyl)morpholine andN-t-pentyloxycarbonyl-4-hydroxypiperidine; and the like.

The photolabile base is exemplified by a compound that includes an anionof a weak acid, and an onium cation that is degradable upon an exposure,and the like. The photolabile base generates in a light-exposed region,a weak acid from: a proton produced through degradation of the oniumcation; and the anion of the weak acid, and thus the acid diffusioncontrollability is lowered.

Examples of the photolabile base include compounds represented by thefollowing formulae, the compound represented by the above formula (3)(wherein, n^(p3) is 0; and R^(p3) and R^(p4) each independentlyrepresent a hydrogen atom or a monovalent hydrocarbon group having 1 to20 carbon atoms), and the like.

In a case in which the radiation-sensitive resin composition containsthe acid diffusion control agent (C), the lower limit of the aciddiffusion control agent (C) with respect to 100 parts by mass of thepolymer component (A) is preferably 0.1 parts by mass, more sopreferably 0.5 parts by mass, and still more preferably 1 part by mass.The upper limit of the content of the acid diffusion control agent (C)is preferably 20 parts by mass, more preferably 10 parts by mass, andstill more preferably 5 parts by mass.

In a case in which the radiation-sensitive resin composition containsthe acid diffusion control agent (C), the lower limit of the content ofthe acid diffusion control agent (C) with respect to 100 mol % of theacid generating agent (B) is preferably 1 mol %, more preferably 5 mol%, and still more preferably 10 mol %. The upper limit of the content ofthe acid diffusion control agent (C) is preferably 250 mol %, morepreferably 150 mol %, and still more preferably 100 mol %.

When the content of the acid diffusion control agent falls within theabove range, more improvements of the inhibitory ability of defects, andthe LWR performance of the radiation-sensitive resin composition areenabled. One, or two or more types of the acid diffusion controller (C)may be contained.

(D) Solvent

The radiation-sensitive resin composition typically contains the solvent(D). The solvent (D) is not particularly limited as long as it is asolvent capable of dissolving or dispersing at least the polymercomponent (A) and the acid generator (B), as well as the optionalcomponent which may be contained as desired.

The solvent (D) is exemplified by an alcohol solvent, an ether solvent,a ketone solvent, an amide solvent, an ester solvent, a hydrocarbonsolvent, and the like.

Examples of the alcohol solvent include:

aliphatic monohydric alcohol solvents having 1 to 18 carbon atoms suchas 4-methyl-2-pentanol and n-hexanol;

alicyclic monohydric alcohol solvents having 3 to 18 carbon atoms suchas cyclohexanol;

polyhydric alcohol solvents having 2 to 18 carbon atoms such as1,2-propylene glycol;

polyhydric alcohol partial ether solvents having 3 to 19 carbon atomssuch as 1-methoxy-2-propanol; and the like.

Examples of the ether solvent include:

dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutylether, dipentyl ether, diisoamyl ether, dihexyl ether and diheptylether;

cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;

aromatic ring-containing ether solvents such as diphenyl ether andanisole; and the like.

Examples of the ketone solvent include:

chain ketone solvents such as acetone, methyl ethyl ketone, methyln-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl iso-butylketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone,di-iso-butyl ketone and trimethylnonanone;

cyclic ketone solvents such as cyclopentanone, cyclohexanone,cycloheptanone, cyclooctanone and methylcyclohexanone;

2,4-pentanedione, acetonylacetone and acetophenone; and the like.

Examples of the amide solvent include:

cyclic amide solvents such as N,N′-dimethylimidazolidinone andN-methylpyrrolidone;

chain amide solvents such as N-methylformamide, N,N-dimethylformamide,N,N-diethylformamide, acetamide, N-methyl acetamide, N,N-dimethylacetamide and N-methylpropionamide; and the like.

Examples of the ester solvent include:

monocarboxylic acid ester solvents such as n-butyl acetate and ethyllactate;

polyhydric alcohol carboxylate solvents such as propylene glycolacetate;

polyhydric alcohol partial ether carboxylate solvents such as propyleneglycol monomethyl ether acetate;

polyhydric carboxylic acid diester solvents such as diethyl oxalate;

carbonate solvents such as dimethyl carbonate and diethyl carbonate; andthe like.

Examples of the hydrocarbon solvent include:

aliphatic hydrocarbon solvents having 5 to 12 carbon atoms such asn-pentane and n-hexane;

aromatic hydrocarbon solvents having 6 to 16 carbon atoms such astoluene and xylene; and the like.

Of these, the ester solvent and/or the ketone solvent are/is preferred,the polyhydric alcohol partial ether carboxylate solvent and/or thecyclic ketone solvent are/is more preferred, and propylene glycolmonomethyl ether acetate and/or cyclohexanone are/is still so morepreferred. One, or two or more types of the solvent (D) may becontained.

Other Optional Component

The other optional component is exemplified by a surfactant, and thelike. The radiation-sensitive resin composition may contain one, or twoor more types of each of the other optional component.

The surfactant exerts the effect of improving the coating property,striation, developability, and the like. Examples of the surfactantinclude: nonionic surfactants such as polyoxyethylene lauryl ether,polyoxyethylene stearyl ether, polyoxyethylene oleyl ether,polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenylether, polyethylene glycol dilaurate and polyethylene glycol distearate;and the like. Examples of the commercially available product of thesurfactant include KP341 (Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75and Polyflow No. 95 (all available from Kyoeisha Chemical Co., Ltd.),EFTOP EF301, EFTOP EF303 and EFTOP EF352 (all available from TochemProducts Co. Ltd.), Megaface F171 and Megaface F173 (all available fromDIC, Corporation), Fluorad FC430 and Fluorad FC431 (all available fromSumitomo 3M Limited), ASAHI GUARD AG710, Surflon S-382, Surflon SC-101,Surflon SC-102, Surflon SC-103, Surflon SC-104, Surflon SC-105 andSurflon SC-106 (all available from Asahi Glass Co., Ltd.), and the like.

In a case in which the radiation-sensitive resin composition containsthe surfactant, the upper limit of the content of the surfactant withrespect to 100 parts by mass of the polymer component (A) is preferably2 parts by mass. The lower limit of the content is, for example, 0.1parts by mass.

Preparation Procedure of Radiation-Sensitive Resin Composition

The radiation-sensitive resin composition may be prepared, for example,by mixing the polymer component (A), the acid generator (B) and thesolvent (D), as well as the optional component which is added as neededsuch as the acid diffusion controller (C) in a certain ratio, andpreferably filtrating the resulting mixture through a membrane filterhaving a pore size of about 0.2 μm.

The radiation-sensitive resin composition may be used either forpositive-tone pattern formation conducted using an alkaline developersolution, or for negative-tone pattern formation conducted using anorganic solvent-containing developer solution.

Resist Pattern-Forming Method

The resist pattern-forming method according to another embodiment of thepresent invention includes: the step of applying directly or indirectlyon a substrate the radiation-sensitive resin composition of theembodiment of the invention (hereinafter, may be also referred to as“applying step”); the step of exposing the resist film formed by theapplying step (hereinafter, may be also referred to as “exposure step”);and the step of developing the resist film exposed (hereinafter, may bealso referred to as “development step”).

Since the radiation-sensitive resin composition of the one embodiment ofthe present invention described above is used in the resistpattern-forming method, formation of a resist pattern being accompaniedby less LWR and fewer defects is enabled, with the sensitivity beingmaintained. Each step will be described below.

Applying Step

In this step, the radiation-sensitive resin composition is applieddirectly or indirectly on the substrate. Thus, a resist film is formed.The substrate is exemplified by a conventionally well-known substratesuch as a silicon wafer, a wafer coated with silicon dioxide oraluminum, and the like. In addition, the case in which theradiation-sensitive resin composition is applied directly on thesubstrate may involve, for example, applying the radiation-sensitiveresin composition on an antireflective film formed on the substrate, andthe like. Such an antireflective film is exemplified by an organic orinorganic antireflective film disclosed in, for example, JapaneseExamined Patent Application, Publication No. H6-12452, JapaneseUnexamined Patent Application, Publication No. S59-93448, and the like.An application procedure is exemplified by spin-coating, cast coating,roll-coating, and the like. After the application, prebaking (PB) may becarried out as needed for evaporating the solvent remaining in thecoating film. The lower limit of the temperature for PB is preferably60° C., and more preferably 80° C. The upper limit of the temperaturefor PB is preferably 150° C., and more preferably 140° C. The lowerlimit of the time period for PB is preferably 5 sec, and more preferably10 sec. The lower limit of the time period for PB is preferably 600 sec,and more preferably 300 sec. The lower limit of the average thickness ofthe resist film formed is preferably 10 nm, and more preferably 20 nm.The upper limit of the average thickness is preferably 1,000 nm, andmore preferably 500 nm.

Exposure Step

In this step, the resist film formed by the applying step is exposed.This exposure is carried out by irradiation with an exposure lightthrough a photomask (as the case may be, through a liquid immersionmedium such as water). Examples of the exposure light includeelectromagnetic waves such as visible light rays, ultraviolet rays, farultraviolet rays, EUV, X-rays and y-rays; charged particle rays such aselectron beams and a-rays, and the like, which may be selected inaccordance with a line width, etc., of the intended pattern. Of these,far ultraviolet rays, EUV or electron beams is preferred; an ArF excimerlaser beam (wavelength: 193 nm), a KrF excimer laser beam (wavelength:248 nm), EUV or an electron beam is more preferred; an ArF excimer laserbeam, EUV or an electron beam is still more preferred; and EUV or anelectron beam is particularly preferred.

It is preferred that post exposure baking (PEB) is carried out after theexposure to promote dissociation of the acid-labile group (a) includedin the polymer component (A), etc. mediated by the acid generated fromthe acid generator (B), etc., upon the exposure in exposed regions ofthe resist film. This PEB enables a difference in solubility of theresist film in a developer solution between the light-exposed regionsand light-unexposed regions to be increased. The lower limit of thetemperature for PEB is preferably 50° C., more preferably 80° C., andstill more preferably 100° C. The upper limit of the temperature ispreferably 180° C., and more preferably 130° C. The lower limit of thetime period for PEB is preferably 5 sec, more preferably 10 sec, andstill more preferably 30 sec. The upper limit of the time period ispreferably 600 sec, more preferably 300 sec, and still more preferably100 sec.

Development Step

In this step, the resist film exposed is developed. Accordingly,formation of a predetermined resist pattern is enabled. After thedevelopment, washing with a rinse agent such as water or an alcohol,followed by drying is typically carried out. The development procedurein the development step may be carried out by either development with analkali, or development with an organic solvent.

In the case of the development with an alkali, the developer solutionfor use in the development is exemplified by alkaline aqueous solutionsprepared by dissolving at least one alkaline compound such as sodiumhydroxide, potassium hydroxide, sodium carbonate, sodium silicate,sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine,diethylamine, di-n-propylamine, triethylamine, methyldiethylamine,ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide(TMAH), pyrrole, piperidine, choline,1,8-diazabicyclo-[5.4.0]-7-undecene, 1,5-diazabicyclo-[4.3.0]-5-nonene,etc., and the like. Of these, an aqueous TMAH solution is preferred, anda 2.38% by mass aqueous TMAH solution is more preferred.

In the case of the development with an organic solvent, the developersolution is exemplified by: an organic solvent such as a hydrocarbonsolvent, an ether solvent, an ester solvent, a ketone solvent and analcohol solvent; a solvent containing the organic solvent; and the like.Exemplary organic solvent includes one, or two or more types of thesolvents exemplified as the solvent (D) for the radiation-sensitiveresin composition, and the like. Of these, the ester solvent or theketone solvent are preferred. The ester solvent is preferably an aceticacid ester solvent, and more preferably n-butyl acetate. The ketonesolvent is preferably a chain ketone, and more preferably 2-heptanone.The lower limit of the content of the organic solvent in the developersolution is preferably 80% by mass, more preferably 90% by mass, stillmore preferably 95% by mass, and particularly preferably 99% by mass.Components other than the organic solvent in the organic solventdeveloper solution are exemplified by water, silicone oil, and the like.

Examples of the development procedure include: a dipping procedure inwhich the substrate is immersed for a given time period in the developersolution charged in a container; a puddle procedure in which thedeveloper solution is placed to form a dome-shaped bead by way of thesurface tension on the surface of the substrate for a given time periodto conduct a development; a spraying procedure in which the developersolution is sprayed onto the surface of the substrate; a dynamicdispensing procedure in which the developer solution is continuouslyapplied onto the substrate that is rotated at a constant speed whilescanning with a developer solution-application nozzle at a constantspeed; and the like.

Examples of the pattern to be formed by the resist pattern-formingmethod include a line-and-space pattern, a hole pattern, and the like.

Polymer Composition

The polymer composition contains the polymer component (A). As referredto herein, the “polymer composition” involves not only a mixture of aplurality of types of polymers, but also one type of polymer. Thepolymer component (A) is as described above as the polymer component (A)contained in the radiation-sensitive resin composition.

EXAMPLES

Hereinafter, the present invention is explained in detail by way ofExamples, but the present invention is not in any way limited to theseExamples. Physical property values in Examples were measured asdescribed below.

Weight-Average Molecular Weight (Mw), Number-Average Molecular Weight(Mn) and Dispersity Index (Mw/Mn)

The Mw and the Mn of the polymer component were determined by gelpermeation chromatography (GPC) using GPC columns (“G2000 HXL” x 2,“G3000 HXL” x 1 and “G4000 HXL” x 1, Tosoh Corporation) under theanalytical conditions involving a flow rate: 1.0 mL/min, an elutionsolvent: tetrahydrofuran, a sample concentration: 1.0% by mass, anamount of injected sample: 100 μL, a column temperature: 40° C., and adetector: differential refractometer, with mono-dispersed polystyrene asa standard. Furthermore, the dispersity index (Mw/Mn) was calculatedfrom the results of the determination of the Mw and the Mn.

Measurement of X1 and X2

By using preparative GPC columns (“JAIGEL 2.5H+2H” available from JapanAnalytical Industry Co., Ltd.) a fraction that corresponds to an areaaccounting for 1% from a shorter retention time was preparativelycollected under analytical conditions involving: a flow rate of 4.0mL/min; an elution solvent of tetrahydrofuran: a sample concentration of3% by mass; an amount of injected sample of 3 mL; a column temperatureof 40° C.; and a detector being a differential refractometer, and thenby using PyGC-MS available from Agilent Technologies, Ltd., an arearatio of each monomer that gives each structural unit was calculated onthe polymer component included in the fraction preparatively collected.Of the area ratio of each monomer, the area ratio of the hydroxystyreneunit was decided as X1 (mol %). Meanwhile, an area ratio of thehydroxystyrene unit determined by a similar analysis on PyGC-MS for theentire polymer component without carrying out the preparative collectionwas decided as X2 (mol %).

Synthesis of Polymer Component (A)

Monomers used in syntheses of the polymer components (A) are presentedbelow.

In Examples described below, unless otherwise specified particularly,values in terms of parts by mass are based on total mass of themonomer(s) used which was assumed to be 100 parts by mass, and values interms of mol % are based on total number of moles of the monomer(s) usedwhich was assumed to account for 100 mol %.

Example 1 Synthesis of Polymer Component (A-1)

The monomer (M-1), the monomer (M-4) and the monomer (M-9) weredissolved in 60 parts by mass of 1-methoxy-2-propanol such that theproportion of each structural unit contained in a polymer finallyobtained (molar ratio) of 35/45/20 was attained. Next, as a chaintransfer agent, 3.5 mol % 2-cyano-2-propyl dodecyl trithiocarbonate withrespect to total monomers, and as a polymerization initiator, 0.7 mol %azobisisobutyronitrile (AIBN) with respect to total monomers were addedto prepare a monomer solution. After the monomer solution was purgedwith nitrogen for 30 min, the monomer solution was heated with stirringto elevate the temperature to 80° C. A time point at which thetemperature of the monomer solution was elevated to 80° C. was regardedas the time point of the start of the polymerization reaction, and thepolymerization reaction was performed for 6 hrs. After completion of thepolymerization reaction, a solution prepared by dissolving 14.3 mol %AIBN with respect to total monomers, and 17.8 mol % tert-dodecanethiolwith respect to total monomers in 50 parts by mass of1-methoxy-2-propanol was added dropwise over 15 min while thetemperature of the polymerization reaction liquid was maintained at 80°C. After completion of the dropwise addition, an end treatment wascarried out by heating at 80° C. for 2 hrs, and then the polymerizationreaction liquid was water-cooled to 30° C. or below.

The cooled polymerization reaction liquid was charged into 500 parts bymass of hexane with respect to 100 parts by mass of the polymerizationreaction liquid, and thus precipitated white powder was filtered off.The white powder obtained by filtration was washed twice with 100 partsby mass of hexane with respect to 100 parts by mass of thepolymerization reaction liquid, followed by filtering off, and dissolvedin 300 parts by mass of 1-methoxy-2-propanol. Next, 500 parts by mass ofmethanol, 50 parts by mass of triethylamine and 10 parts by mass ofultra pure water were added to the solution, and a hydrolysis reactionwas performed with stirring at 70° C. for 6 hrs.

After completion of the reaction, a remaining solvent was distilledaway, and the solid thus obtained was dissolved in 100 parts by mass ofacetone. The solution was added dropwise into 500 parts by mass of waterto allow coagulation of the polymer, and the solid thus obtained wasfiltered off. Moreover, 3,000 parts by mass of butyl acetate were addedto the solid to permit dissolution, and the solid was washed with 3,000parts by mass of a 5% so by mass aqueous sodium bicarbonate solution.Subsequently, the organic layer was washed three times with 3,000 partsby mass of ultra pure water, and the concentrated until the amount wasreduced to 300 parts by mass with respect to total monomers. Thusresulting concentrate was added dropwise into five-times mass of hexaneto allow coagulation of the polymer, which was dried at 50° C. for 12hrs to give a white powdery polymer component (A-1).

Examples 2 to 6 Syntheses of Polymer Components (A-2) to (A-6)

Polymer components (A-2) to (A-6) were synthesized in a similar mannerto Example 1 except that each monomer of the type and the proportionshown in Table 1 below was used. In Table 1, “-” indicates that thecorresponding monomer was not used.

Example 7 Synthesis of Polymer Component (A-7)

The monomer (M-1), the monomer (M-4) and the monomer (M-9) weredissolved in 200 parts by mass of 1-methoxy-2-propanol such that theproportion of each structural unit contained in a polymer finallyobtained (molar ratio) of 35/45/20 was attained. Next, as apolymerization initiator, 5 mol % AIBN with respect to total monomerswas added to prepare a monomer solution. Meanwhile, after a vacantreaction vessel was purged with nitrogen for 30 min, 100 parts by massof 1-methoxy-2-propanol were added thereto, and heated with stirring toelevate the temperature to 80° C. Subsequently, the monomer solutionprepared as described above was added dropwise over 3 hrs, andthereafter the mixture was further heated at 80° C. for 3 hrs, whereby apolymerization reaction was performed for 6 hrs in total. polymerizationAfter completion of the reaction, polymerization reaction liquid waswater-cooled to 30° C. or below.

The cooled polymerization reaction liquid was charged into 500 parts bymass of hexane with respect to 100 parts by mass of the polymerizationreaction liquid, and thus precipitated white powder was filtered off.The white powder obtained by filtration was so washed twice with 100parts by mass of hexane with respect to 100 parts by mass of thepolymerization reaction liquid, followed by filtering off, and dissolvedin 300 parts by mass of 1-methoxy-2-propanol. Next, 500 parts by mass ofmethanol, 50 parts by mass of triethylamine and 10 parts by mass ofultra pure water were added to the solution, and a hydrolysis reactionwas performed with stirring at 70° C. for 6 hrs.

After completion of the reaction, a remaining solvent was distilledaway, and the solid thus obtained was dissolved in 100 parts by mass ofacetone. The solution was added dropwise into 500 parts by mass of waterto allow coagulation of the polymer, and the solid thus obtained wasfiltered off. Moreover, 3,000 parts by mass of butyl acetate were addedto the solid to permit dissolution, and the solid was washed with 3,000parts by mass of a 5% by mass aqueous sodium bicarbonate solution.Subsequently, the organic layer was washed three times with 3,000 partsby mass of ultra pure water, and the concentrated until the amount wasreduced to 300 parts by mass with respect to total monomers. Thusresulting concentrate was added dropwise into five-times mass of hexaneto allow coagulation of the polymer, which was dried at 50° C. for 12hrs to give a white powdery polymer component (A-7).

Examples 8 to 10 Syntheses of Polymer Components (A-8) to (A-10)

Polymer components (A-8) to (A-10) were synthesized in a similar mannerto Example 7 except that each monomer of the type and the proportionshown in Table 1 below was used.

Example 11 Purification of Polymer Component (A-1) by Preparative GPC

The polymer component (A-1) was purified by using preparative GPCavailable from GL Sciences, Inc., to remove: a fraction corresponding toa cumulative area accounting for 25% of a total area on the GPC elutioncurve from a shorter retention time; and a fraction corresponding to acumulative area accounting for 25% of a total area on the GPC elutioncurve from a longer retention time, whereby a remainder fraction (afraction corresponding to a cumulative area accounting for 25% to 75% ofthe total area on the GPC elution area) was preparatively collected togive a polymer component (A-1P). It is to be noted that the total areaof the GPC elution curve was assumed to be 100%.

Reference Synthesis Examples 1 to 2 Syntheses of Polymer Components(A-11) to (A-12)

Polymer components (A-11) to (A-12) were synthesized in a similar mannerto Example 7 except that each monomer of the type and the proportionshown in Table 1 below was used.

Examples 12 to 14 Syntheses of Polymer Components (A-13) to (A-15)

Polymer components (A-13) to (A-15) were synthesized in a similar mannerto Example 7 except that each monomer of the type and the proportionshown in Table 1 below was used.

Comparative Synthesis Example 1 Synthesis of Polymer Component (a-1)

The monomer (M-1), the monomer (M-4) and the monomer (M-9) weredissolved in 60 parts by mass of 1-methoxy-2-propanol such that theproportion of each structural unit contained in a polymer finallyobtained (molar ratio) of 35/45/20 was attained. Next, as a chaintransfer agent, 3.5 mol % 2-cyano-2-propyl dodecyl trithiocarbonate withrespect to total monomers, and as a polymerization initiator, 0.7 mol %AIBN with respect to total monomers were added to prepare a monomersolution. After being purged with nitrogen for 30 min, the monomersolution was heated with stirring to elevate the temperature to 80° C. Atime point at which the temperature of the monomer solution was elevatedto 80° C. was regarded as the time point of the start of thepolymerization reaction, and the polymerization reaction was performedfor 6 hrs. After completion of the polymerization reaction, a solutionprepared by dissolving 14.3 mol % AIBN with respect to total monomers,and 17.8 mol % tert-dodecanethiol with respect to total monomers in 60parts by mass of 1-methoxy-2-propanol was added dropwise over 15 minwhile the temperature of the polymerization reaction liquid wasmaintained at 80° C. After completion of the dropwise addition, an endtreatment was carried out by heating at 80° C. for 2 hrs, and then thepolymerization reaction liquid was water-cooled to 30° C. or below.

The cooled polymerization reaction liquid was charged into 500 parts bymass of hexane with respect to 100 parts by mass of the polymerizationreaction liquid, and thus precipitated white powder was filtered off.The white powder obtained by filtration was washed twice with 100 partsby mass of hexane with respect to 100 parts by mass of thepolymerization reaction liquid, followed by filtering off, and dissolvedin 300 parts by mass of 1-methoxy-2-propanol. Next, 500 parts by mass ofmethanol, 50 parts by mass of triethylamine and 10 parts by mass ofultra pure water were added to the solution, and a hydrolysis reactionwas performed with stirring at 70° C. for 6 hrs.

After completion of the reaction, remaining solvent was distilled away,and the solid thus obtained was dissolved in 100 parts by mass ofacetone. The solution was added dropwise into 500 parts by mass of waterto allow coagulation of the polymer, and the solid thus obtained wasfiltered off. Drying at 50° C. for 12 hrs gave a white powdery polymercomponent (a-1).

Comparative Synthesis Examples 2 to 4 Syntheses of Polymer Components(a-2) to (a-4)

Polymer components (a-2) to (a-4) were synthesized in a similar mannerto Comparative Synthesis Example 1 except that each monomer of the typeand the proportion shown in Table 1 below was used.

Comparative Synthesis Example 5 Synthesis of Polymer Component (a-5)

The monomer (M-1), the monomer (M-4) and the monomer (M-11) weredissolved in 200 parts by mass of 1-methoxy-2-propanol such that theproportion of each structural unit contained in a polymer finallyobtained (molar ratio) of 50/30/20 was attained. Next, as apolymerization initiator, 5 mol % AIBN with respect to total monomerswas added to prepare a monomer solution. Meanwhile, after a vacantreaction vessel was purged with nitrogen for 30 min, 100 parts by massof 1-methoxy-2-propanol were added thereto, and heated with stirring toelevate the temperature to 80° C. Subsequently, the monomer solutionprepared as described above was added dropwise over 3 hrs, andthereafter the mixture was further heated at 80° C. for 3 hrs, whereby apolymerization reaction was performed for 6 hrs in total. polymerizationAfter completion of the reaction, polymerization reaction liquid waswater-cooled to 30° C. or below.

The cooled polymerization reaction liquid was charged into 500 parts bymass of hexane with respect to 100 parts by mass of the polymerizationreaction liquid, and thus precipitated white powder was filtered off.The white powder obtained by filtration was washed twice with 100 partsby mass of hexane with respect to 100 parts by mass of thepolymerization reaction liquid, followed by filtering off, and dissolvedin 300 parts by mass of 1-methoxy-2-propanol. Next, 500 parts by mass ofmethanol, 50 parts by mass of triethylamine and 10 parts by mass ofultra pure water were added to the solution, and a hydrolysis reactionwas performed with stirring at 70° C. for 6 hrs.

After completion of the reaction, remaining solvent was distilled away,and the solid thus obtained was dissolved in 100 parts by mass ofacetone. The solution was added dropwise into 500 parts by mass of waterto allow coagulation of the polymer, and the solid thus obtained wasfiltered off, which was dried at 50° C. for 12 hrs to give a whitepowdery polymer component (a-5).

Comparative Synthesis Examples 6 to 8: Syntheses of Polymer Components(a-6) to so (a-8)

Polymer components (a-6) to (a-8) were synthesized in a similar mannerto Comparative Synthesis Example 5 except that each monomer of the typeand the proportion shown in Table 1 below was used.

TABLE 1 Monomer Monomer Monomer that gives that gives that givesstructural structural other unit (I) unit (II) structural unit (A)Polymer proportion proportion proportion Yield X1 X2 component type (mol%) type (mol %) type (mol %) (%) Mw Mw/Mn (mol %) (mol %) X2/X1 Example1 A-1 M-1 35 M-4 45 M-9 20 77 5,600 1.29 35.1 37.2 1.06 Example 2 A-2M-1 40 M-4 10 M-10 50 78 5,800 1.27 39.2 44.7 1.14 Example 3 A-3 M-1 30M-5 20 M-11 20 73 6,100 1.27 28.8 30.5 1.06 M-7 30 Example 4 A-4 M-2 35M-6 15 M-12 50 76 5,900 1.28 35.0 37.2 1.06 Example 5 A-5 M-1 55 M-7 45— — 78 5,700 1.28 55.2 57.4 1.04 Example 6 A-6 M-1 40 M-5 30 M-11 10 805,800 1.20 38.6 43.8 1.13 M-7 20 Example 7 A-7 M-1 35 M-4 45 M-9 20 806,000 1.55 45.5 46.1 1.01 Example 8 A-8 M-3 45 M-8 55 — — 80 6,900 1.5436.8 38.9 1.06 Example 9 A-9 M-2 25 M-4 15 M-10 20 79 6,800 1.56 26.528.8 1.09 M-5 40 Example 10 A-10 M-3 40 M-7 60 — — 79 6,900 1.55 42.746.9 1.10 Example 11 A-1P M-1 35 M-4 45 M-9 20 35 5,600 1.19 37.0 37.21.01 Reference A-11 M-1 100  — — — — 80 5,000 1.51 100.0  100.0  1.00Synthesis Example 1 Reference A-12 — — M-7 100  — — 80 5,500 1.52 — — —Synthesis Example 2 Example 12 A-13 M-1 20 M-5 60 — — 80 5,300 1.55 38.742.1 1.09 M-13 20 Example 13 A-14 M-1 20 M-5 60 — — 75 5,100 1.53 38.241.6 1.09 M-14 20 Example 14 A-15 M-1 20 M-5 60 — — 70 5,500 1.50 36.340.1 1.10 M-15 20 Comparative a-1 M-1 35 M-4 45 M-9 20 85 5,600 1.2939.1 37.2 0.95 Synthesis Example 1 Comparative a-2 M-1 30 M-5 20 — — 735,800 1.27 32.1 30.1 0.94 Synthesis M-6 20 Example 2 M-7 30 Comparativea-3 M-2 35 M-7 15 M-9 50 76 5,900 1.28 37.9 35.4 0.93 Synthesis Example3 Comparative a-4 M-3 40 M-4 60 — — 78 6,000 1.28 55.3 44.2 0.80Synthesis Example 4 Comparative a-5 M-1 50 M-4 30 M-11 20 80 6,700 1.5553.2 49.2 0.92 Synthesis Example 5 Comparative a-6 M-1 40 M-4 30 M-11 3078 7,000 1.55 43.7 40.9 0.94 Synthesis Example 6 Comparative a-7 M-2 25M-8 15 M-10 40 79 6,800 1.56 26.7 24.3 0.91 Synthesis M-12 20 Example 7Comparative a-8 M-3 60 M-4 40 — — 79 6,900 1.55 63.2 61.2 0.97 SynthesisExample 8

Preparation of Radiation-Sensitive Resin Composition

The acid generating agent (B), the acid diffusion control agent (C) andthe solvent (D) used for preparing the radiation-sensitive resincompositions are shown below.

(B) Acid Generating Agent

B-1 to B-6: compounds represented by the following formulae (B-1) to(B-6)

(C) Acid Diffusion Control Agent

C-1 to C-4: compounds represented by the following formulae (C-1) to(C-4)

(D) Solvent

D-1: propylene glycol monomethyl ether acetate

D-2: cyclohexanone

Example 15

A radiation-sensitive resin composition (R-1) was prepared by: mixing100 parts by mass of (A-1) as the polymer component (A), 20 parts bymass of (B-1) as the acid generating agent (B), 30 mol % (C-1), withrespect to (B-1), as the acid diffusion control agent (C), 4,800 partsby mass of (D-1) and 2,000 parts by mass of (D-2) as the solvent (D);and then filtering a thus obtained mixture through a membrane filterhaving a pore size of 0.2 μM

Examples 16 to 36 and Comparative Examples 1 to 10

Radiation-sensitive resin compositions (R-2) to (R-22) and (CR-1) to(CR-10) were prepared by a similar operation to that of Example 15except that each component of the type and the content shown in Table 2below was used. It is to be noted that in preparing theradiation-sensitive resin composition (R-19), measurements of X1 and X2conducted on the mixture obtained by mixing 50 parts by mass of (A-11)and 50 parts by mass of (A-12) revealed inequalities of X1<X2, andX2/X1>1.0. In Example 33, parts by mass of this mixture were used as thepolymer component (A).

TABLE 2 (C) Acid diffusion control (A) Polymer (B) Acid generating agentRadiation- component agent content (mol % (D) Solvent sensitive content(parts content (parts with respect to (B) content (parts by compositionType by mass) type by mass) type component) type mass) Example 15 R-1A-1 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000 Example 16 R-2 A-1 100 B-3 20C-3 30 D-1/D-2 4,800/2,000 Example 17 R-3 A-1 100 B-2 20 C-1 30 D-1/D-24,800/2,000 Example 18 R-4 A-2 100 B-4 20 C-2 30 D-1/D-2 4,800/2,000Example 19 R-5 A-2 100 B-5 20 C-1 30 D-1/D-2 4,800/2,000 Example 20 R-6A-3 100 B-3 20 C-1 30 D-1/D-2 4,800/2,000 Example 21 R-7 A-3 100 B-6 20C-4 30 D-1/D-2 4,800/2,000 Example 22 R-8 A-4 100 B-1 20 C-1 30 D-1/D-24,800/2,000 Example 23 R-9 A-4 100 B-2 20 C-4 30 D-1/D-2 4,800/2,000Example 24 R-10 A-5 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000 Example 25R-11 A-6 100 B-4 20 C-2 30 D-1/D-2 4,800/2,000 Example 26 R-12 A-7 100B-2 20 C-3 30 D-1/D-2 4,800/2,000 Example 27 R-13 A-8 100 B-3 20 C-1 30D-1/D-2 4,800/2,000 Example 28 R-14 A-8 100 B-4 20 C-1 30 D-1/D-24,800/2,000 Example 29 R-15 A-9 100 B-5 20 C-2 30 D-1/D-2 4,800/2,000Example 30 R-16 A-10 100 B-1 20 C-3 30 D-1/D-2 4,800/2,000 Example 31R-17 A-1P 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000 Example 32 R-18 A-1P 100B-2 20 C-3 30 D-1/D-2 4,800/2,000 Example 33 R-19 A-11 50 B-1 20 C-1 30D-1/D-2 4,800/2,000 A-12 50 Example 34 R-20 A-13 100 B-1 20 C-1 30D-1/D-2 4,800/2,000 Example 35 R-21 A-14 100 B-1 20 C-1 30 D-1/D-24,800/2,000 Example 36 R-22 A-15 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000Comparative CR-1 a-1 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000 Example 1Comparative CR-2 a-1 100 B-2 20 C-3 30 D-1/D-2 4,800/2,000 Example 2Comparative CR-3 a-2 100 B-4 20 C-2 30 D-1/D-2 4,800/2,000 Example 3Comparative CR-4 a-3 100 B-2 20 C-3 30 D-1/D-2 4,800/2,000 Example 4Comparative CR-5 a-4 100 B-3 20 C-1 30 D-1/D-2 4,800/2,000 Example 5Comparative CR-6 a-5 100 B-4 20 C-2 30 D-1/D-2 4,800/2,000 Example 6Comparative CR-7 a-6 100 B-5 20 C-1 30 D-1/D-2 4,800/2,000 Example 7Comparative CR-8 a-7 100 B-3 20 C-1 30 D-1/D-2 4,800/2,000 Example 8Comparative CR-9 a-8 100 B-6 20 C-4 30 D-1/D-2 4,800/2,000 Example 9Comparative CR-10 a-8 100 B-1 20 C-1 30 D-1/D-2 4,800/2,000 Example 10

Resist Pattern Formation

By using a spin coater (Tokyo Electron Limited, “CLEAN TRACK ACTS”), theradiation-sensitive resin composition prepared as described above wasapplied on the surface of an 12-inch silicon wafer coated with AL412(Brewer Science, Inc.) having a film thickness of 20 nm, and subjectedto PB at 130° C. for 60 sec, followed by cooling at 23° C. for 30 sec togive a resist film having a film thickness of 55 nm. Next, this resistfilm was irradiated with EUV light using an EUV scanner (model“NXE3300”, manufactured by ASML, NA=0.33, irradiation conditions:Conventional s=0.89, mask imec DEFECT 32 FFR02). Subsequently, PEB wascarried out at 110° C. for 60 sec, followed by cooling at 23° C. for 30sec, and a development with a 2.38% by mass aqueous TMAH solution at 23°C. for 30 sec to form a positive-tone 32-nm line-and-space pattern

Evaluations

The inhibitory ability of defects, and the sensitivity and the LWRperformance of the radiation-sensitive resin compositions were evaluatedaccording to the following methods. For line-width measurement in theevaluations of the sensitivity and the LWR performance of the resistpattern, High-Resolution FEB line-width measurement apparatus (“CG5000”,Hitachi High-Technologies Corporation) was used.

Inhibitory Ability of Defects

On the line-and-space pattern formed as described above, the number ofdefects (number/cm²) was measured using a defect inspection system(“KLA2925”, KLA-Tencor Corporation). The inhibitory ability of defectswas evaluated to be: “favorable” in a case of being no greater than20/cm²; and “unfavorable” in a case of being greater than 20/cm².

Sensitivity

In the resist pattern formation, an exposure dose at which the 32-nmline-and-space pattern was formed was regarded as optimum exposure dose,and this optimum exposure dose was defined as “sensitivity (mJ/cm²)”.

LWR Performance

The 32-nm line-and-space pattern formed as described above was observedfrom above the pattern, and the line width was measured at arbitrary 50points. Then a 3 Sigma value was determined from the distribution of themeasurements, and the 3 Sigma value was defined as “LWR performance(nm)”. The smaller value reveals less variance of the line width,indicating a better LWR performance. The LWR performance was evaluatedto be: “favorable” in a case of being no greater than 3.1 nm; and“unfavorable” in a case of being greater than 3.1 nm.

TABLE 3 Inhibitory Radiation- ability of LWR sensitive defectsSensitivity performance composition (number/cm²) (mJ/cm²) (nm) Example15 R-1 9 42 2.8 Example 16 R-2 8 35 2.7 Example 17 R-3 5 42 2.8 Example18 R-4 6 48 2.6 Example 19 R-5 2 46 2.7 Example 20 R-6 4 37 2.9 Example21 R-7 5 49 3.0 Example 22 R-8 6 46 2.7 Example 23 R-9 3 31 2.9 Example24 R-10 13 38 3.1 Example 25 R-11 5 48 2.7 Example 26 R-12 6 46 2.6Example 27 R-13 3 49 2.5 Example 28 R-14 5 41 2.3 Example 29 R-15 7 432.5 Example 30 R-16 11 38 3.0 Example 31 R-17 9 44 2.9 Example 32 R-18 936 2.7 Example 33 R-19 20 42 3.5 Example 34 R-20 5 40 3.3 Example 35R-21 11 45 3.0 Example 36 R-22 9 50 2.5 Comparative CR-1 75 42 3.5Example 1 Comparative CR-2 102 35 3.2 Example 2 Comparative CR-3 89 463.2 Example 3 Comparative CR-4 110 42 3.5 Example 4 Comparative CR-5 16437 3.6 Example 5 Comparative CR-6 98 46 3.4 Example 6 Comparative CR-7132 45 3.6 Example 7 Comparative CR-8 126 46 3.8 Example 8 ComparativeCR-9 92 42 3.9 Example 9 Comparative CR-10 194 40 3.8 Example 10

As is clear from the results shown in Table 3, the radiation-sensitiveresin compositions of Examples were all superior in the inhibitoryability of defects, and the LWR performance. Also, theradiation-sensitive resin composition prepared by using the polymercomponent (A-1P) obtained through purification on preparative GPCexhibited equivalent inhibitory ability of defects, and the LWRperformance.

INDUSTRIAL APPLICABILITY

The radiation-sensitive resin composition and the resist pattern-formingmethod of o the embodiments of the present invention enable a resistpattern with less LWR and fewer defects to be formed, while thesensitivity is maintained. The polymer component of the embodiment ofthe present invention can be suitably used as a component of theradiation-sensitive resin composition of the embodiment of theinvention. Therefore, these can be suitably used in manufacture ofsemiconductor devices in which further progress of miniaturization isexpected in the future.

What is claimed is:
 1. A radiation-sensitive resin composition whichcomprises: a polymer component comprising in a single polymer ordifferent polymers, a first structural unit that comprises a phenolichydroxyl group and a second structural unit that comprises anacid-labile group; and a radiation-sensitive acid generator, wherein,the polymer component satisfies inequality (A):X1<X2   (A) wherein, in the inequality (A), X1 represents a proportion(mol %) of the first structural unit comprised with respect to totalstructural units constituting the polymer component comprised in afraction eluted until a retention time at which a cumulative areaaccounts for 1% of a total area on a gel permeation chromatography (GPC)elution curve of the polymer component detected by a differentialrefractometer; and X2 represents a proportion (mol %) of the firststructural unit comprised with respect to total structural unitsconstituting the polymer component.
 2. A radiation-sensitive resincomposition which comprises: a polymer component comprising in a singlepolymer or different polymers, a first structural unit that comprises aphenolic hydroxyl group and a second structural unit that comprises anacid-labile group; and a radiation-sensitive acid generator, wherein,the polymer component satisfies inequality (B): $\begin{matrix}{\frac{X\; 2}{X\; 1} > 1.0} & (B)\end{matrix}$ wherein, in the inequality (B), X1 represents a proportion(mol %) of the first structural unit comprised with respect to totalstructural units constituting the polymer component comprised in afraction eluted until a retention time at which a cumulative areaaccounts for 1% of a total area on a gel permeation chromatography (GPC)elution curve of the polymer component detected by a differentialrefractometer; and X2 represents a proportion (mol %) of the firststructural unit comprised with respect to total structural unitsconstituting the polymer component.
 3. The radiation-sensitive resincomposition according to claim 1, wherein the first structural unit isrepresented by formula (1):

wherein, in the formula (1), R¹ represents a hydrogen atom, a fluorineatom, a methyl group or a trifluoromethyl group; R²represents a singlebond, —O—, —COO—* or —CONH—*, wherein * denotes a binding site to Ar; Arrepresents a group obtained from an arene having 6 to 20 ring atoms byremoving (p+q+1) hydrogen atoms on the aromatic ring; p is an integer of0 to 10, wherein in a case in which p is 1, R³ represents a monovalentorganic group having 1 to 20 carbon atoms or a halogen atom, and in acase in which p is no so less than 2, a plurality of R³s are identicalor different, and each represent a monovalent organic group having 1 to20 carbon atoms or a halogen atom, or at least two of the plurality ofR³s taken together represent a part of a ring structure having 4 to 20ring atoms together with the carbon atom to which the at least two ofthe plurality of R³s bond; and q is an integer of 1 to 11, wherein (p+q)is no greater than
 11. 4. The radiation-sensitive resin compositionaccording to claim 1, wherein the second structural unit is representedby formula (2-1A), formula (2-1B), formula (2-1C), formula (2-2A) orformula (2-2B):

wherein, in the formulae (2-1A), (2-1B), (2-1C), (2-2A) and (2-2B),R^(T)s each independently represent a hydrogen atom, a fluorine atom, amethyl group or a trifluoromethyl group: in the formulae (2-1A) and(2-1B), R^(X)s each independently represent a monovalent hydrocarbongroup having 1 to 20 carbon atoms; R^(Y) and R^(Z) each independentlyrepresent a monovalent hydrocarbon group having 1 to 20 carbon atoms, orR^(Y) and R^(Z) taken together represent a part of an alicyclicstructure having 3 to 20 ring atoms together with the carbon atom towhich R^(Y) and R^(Z) bond. in the formula (2-1C), R^(A) represents ahydrogen atom; R^(B) and R^(C) each independently represent a hydrogenatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms;R^(D) represents a divalent hydrocarbon group having 1 to 20 carbonatoms constituting an unsaturated alicyclic structure having 4 to 20ring atoms together with the carbon atoms to which R^(A), R^(B) andR^(C) each bond; in the formulae (2-2A) and (2-2B), R^(U) and R^(V) eachindependently represent a hydrogen atom or a monovalent hydrocarbongroup having 1 to 20 carbon atoms; R^(W)s each independently represent amonovalent hydrocarbon group having 1 to 20 carbon atoms, or R^(U) andR^(V) taken together represent a part of an alicyclic structure having 3to 20 ring atoms together with the carbon atom to which R^(U) and R^(V)bond, or R^(U) and R^(W) taken together represent a part of an aliphaticheterocyclic structure having 5 to 20 ring atoms together with thecarbon atom to which R^(U) bonds and the oxygen atom to which R^(W)bonds.
 5. The radiation-sensitive resin composition according to claim1, wherein the polymer component further comprises other structural unitthan the first structural unit or the second structural unit.
 6. Theradiation-sensitive resin composition according to claim 1, wherein aratio of a polystyrene-equivalent weight-average molecular weight asdetermined by gel permeation chromatography to a polystyrene-equivalentnumber-average molecular weight of the polymer component as determinedby gel permeation chromatography is no less than 1.4.
 7. A resistpattern-forming method comprising: applying the radiation-sensitiveresin composition according to claim 1 directly or indirectly on asubstrate; exposing a resist film provided by the applying; anddeveloping the resist film exposed.
 8. A polymer composition whichcomprises a polymer component comprising in a single polymer ordifferent polymers, a first structural unit that comprises a phenolichydroxyl group and a second structural unit that comprises anacid-labile group, wherein, the polymer component satisfies inequality(A):X1<X2   (A) wherein, in the inequality (A), X1 represents a proportion(mol %) of the first structural unit comprised with respect to totalstructural units constituting the polymer component comprised in afraction eluted until a retention time at which a cumulative areaaccounts for 1% of a total area on a gel permeation chromatography (GPC)elution curve of the polymer component detected by a differentialrefractometer; and X2 represents a proportion (mol %) of the firststructural unit comprised with respect to total structural unitsconstituting the polymer component.
 9. A polymer composition whichcomprises a polymer component comprising in a single polymer ordifferent polymers, a first structural unit that comprises a phenolichydroxyl group and a second structural unit that comprises anacid-labile group, the polymer component satisfies inequality (B):$\begin{matrix}{\frac{X\; 2}{X\; 1} > 1.0} & (B)\end{matrix}$ wherein, in the inequality (B), X1 represents a proportion(mol %) of the first structural unit comprised with respect to totalstructural units constituting the polymer component comprised in afraction eluted until a retention time at which a cumulative areaaccounts for 1% of a total area on a gel permeation chromatography (GPC)elution curve of the polymer component detected by a differentialrefractometer; and X2 represents a proportion (mol %) of the firststructural unit comprised with respect to total structural unitsconstituting the polymer component.